The easiest way to think of how the Netflix deal works is to compare it to the Hulk situation. Though even there, it is not exactly the same but they share similarities. Marvel TV makes the Netflix shows. Netflix is a distributor in this case. Just like how with a Hulk movie, Universal gets the choice to distribute the movie. If Netflix declined the shows, Marvel could look elsewhere for distribution (usually how it works...see how they shopped Agent Carter to Netflix when it was cancelled, though they declined picking it up). But the big thing is Netflix doesn't make Daredevil, JJ, Luke Cage, Iron Fist, etc. Marvel makes them.
Now, why is Marvel more ok giving Netflix these shows and not allowing Universal to make a Hulk film? The Netflix characters are more mature related programming. Less friendly to Disney's or Marvel's overall brand. Hulk can sell toys like Cap or Iron Man. So Marvel is okay allowing the edgier programming on Netflix as it gets them acclaim and protects their brand.