You're love of Ennis' excellent run is blinding you to the facts that the comic book industry has changed dramatically in the past decade. We are now in an industry where the only Marvel characters that can handle solo titles are Spider-Man, Wolverine, Hulk, Iron Man, Captain America, Thor, and Daredevil. We are now in an industry where no Marvel character can handle two titles.
The Punisher just doesn't sell anymore dude. No matter who writes him. Greg Rucka's Punisher is selling dramatically lower than Rick Remender's run (both of whom are great writers and deliver great Punisher stories). Six issues in and the current Punisher book is on the verge of entering cancellation territory. PunisherMAX got canned due to absurdly low sales, despite a great creative team (Steve Dillon one of Ennis' artists BTW).