Because that other company would pay for it. Freeform and ABC are owned by Disney, if both those and Disney's new streaming service pass on a Marvel show then that show doesn't happen unless they can pitch it to another network. The downside would be Disney wouldn't get 100% of the revenue, the upside is that ABC, Freeform, and their streaming service doesn't loose content, just keeps making different content but they also have to pay for the production. Having it on a different network means they get less revenue but don't put up the production costs. For example, Netflix are paying Marvel/Disney to make the Defender shows.
So it is a question of If we're not gonna be making 100% of the revenue, would we settle for 25% without having to put up production costs, or just get nothing by not making a series. I wouldn't be surprise if Disney wants everything in house but also would be surprised if they have a "right of first refusal" policy. Meaning Marvel has to pitch it to Disney owned networks first and then get the okay to shop it around.
I've also heard talk that spin-offs of existing series can happen. I'm hoping that Moon Knight appears in a future season just so he can be part of the Netflix side.
Anyway, for the Disney streaming service, I hope that these are the series we get.
Series set in and around New York City
She-Hulk - Ally McBeal with superpowers and occasional fights with Titania with Mark Ruffalo and Charlie Cox popping up to cameo once in a while. I'd put it in Staten Island since it's a sleepier borough and no hero is based there yet.
Ms. Marvel - A coming of age story with an occasional Brie Larson cameo about a young teenage girl getting superpowers. Set in New Jersey.
Hawkeye - Because unlike Black Widow and War Machine, I can't see him getting his own film. He's grounded enough to do on TV. What matters is that we get to see Hawkeye get his own stories based on the Matt Fraction run. Set in Brooklyn.
Marvel Horror (Because Disney owns Touchstone and distributes Dreamworks and some of those films are Rated R. Disney buying Fox would also mean a ton of R-rated films which Disney would be stupid to not stream in-house since EVERYBODY loves the original Predator. Adult-oriented horror properties would be great to have.)
Ghost Rider - Set in Los Angeles. Johnny's story of revenge on The Orb told from Robbie's perspective for Season 1. Based heavily on the Michael Fleisher and Felipe Smith runs. Season 2 is The story of Johnny passing the torch on to Robbie while fighting Centurious, Earl Gustav, Kazann and Ruth and based heavily on the J.M. DeMatties and Garth Ennis runs. Johnny's half-brother winds up becoming a Ghost Rider in the last shot. Robbie becoming the mentor to Dan in Season 3 as Robbie hunts Deathwatch and Dan learns the ropes while tracking down Scarecrow. Deathwatch kills Roxanne Simpson. Based heavily on the Howard Mackie run. Season 4 has Robbie heading south of the border where he investigates a human trafficking ring run by the biblical Adam and a man named Jones along with their bodyguards Steel Wind and Steel Vengeance. Along the way Robbie will meet a sex slave named Alejandra and turn her into a new Ghost Rider. Blackheart resurrects Roxanne Simpson as Black Rose and Dan is powerless to stop them. The only way to defeat Blackheart is for Johnny to once again become a Ghost Rider. Based on the Rob Williams and Ivan Velez runs. Season 5 has all four Ghost Riders summoned to heaven for God has fallen and Zadkiel has forgiven all the fallen angels who may now return home. But Zarathos has other plans and won't stand for a usurper upon heaven's throne. Guest starring Angela. Based on the Jason Aaron run. Blackout won't be redone since we got a comic-accurate Blackout in Ghost Rider: Spirit of Vengeance but Blackheart looked nothing like his comic counterpart and needs to be redone.
Blade: The Tomb of Dracula - Set in New Orleans. A young woman named Rachel Van Helsing seeks out a team of paranormal investigators named the Nightstalkers to inform them that Dracula has returned. Focuses more on Blade as a hero who hunts with a strong detective angle and Dracula often having a strong sympathetic streak despite him being the prey/a villain. Season 2 would feature Deacon Frost. Season 3 would have Lucas Cross as the villain. Season 4 would feature Doctor Sun. If Marvel does get the X-Men rights back, then Xarus is a possibility for Season 2 instead of Frost. Dracula would survive every season and prove to be an interesting antagonist for Blade.
Man-Thing - Set in Miami. Stephanie Szostak returns as Ellen Brandt from Iron Man 3 who survived the events of the film due to her healing factor (but has a nasty scar thanks to Tony Stark) and who spends the series hunting down her mutated ex-husband. Ted Sallis is now a swamp monster and incapable of speech and looks like a shrub but still retains his soul. Hunted down by AIM in South Florida, Ted must rediscover his humanity.
Werewolf by Night - Comics take place in LA but I'd rather see it moved to Las Vegas, Phoenix or San Diego to move him away from Ghost Rider. Cursed by the Darkhold by Dracula as a child, Jack Russel is turned into a werewolf and must go on the run to protect himself and those he loves. He must find a way to retain his mind during his transformations so he may reclaim his life.
Midnight Sons - Set in Dallas. The Ghost Riders (and allies Jennifer Kale, Satana and Damien Hellstrom), The Nightstalkers, Man-Thing and Werewolf by Night must team up to stop Mephisto.
Agents of SHIELD spin-offs/continuations
Shang-Chi - Set in Hong Kong. A young MMA cage fighter learns that his fights are being fixed by the Si Fan triad and is recriuted by SHIELD who at first attempt to arrest him. A pure Hong Kong gangster film in the style of John Woo with white-knuckled martial arts action. Featuring the villainy of Zheng Zu (Marvel's current name for Fu Manchu), Cursed Lotus, M'Nai and Moving Shadow as Shang Chi's villainous family and their current hitman the Taskmaster. Season 2 would have Carlton Velcro, Pavane and Razorfist. Season 3 would feature Shockwave. SHEILD's Hong Kong branch would be made up of Denis Nyland Smith and Blackjack with cameos from May and Quake.
Mockingbird - Marvel's Most Wanted gets new life on Disney's streaming service. Villains are original characters who are part of HYDRA and AIM.