As much as I like the show, Marvel's Agents of S.H.I.E.L.D. is not doing all that well in the ratings. CW is doing well with their DC stuff, but no one else really seems to be able to get a good property going. I really hope I'm wrong, and The Phil Coulson Show gets a second season.
Point being, the "big" networks aren't seeing much success with the genre. It's not a bad idea, but it's a hard one to sell.