I guess not having time for them anymore? It's still gonna be some years until that day, but when (that's WHEN, not IF) I become a game designer, I'm unlikely to have much time left for comics, especially when the comics are just something I do as a hobby for fun. I wanna do both, dammit!
Also, as a creator (in general) I'd be really worried about getting published by a company and them "owning" my series, characters ect, unless it's specifically supposed to be a one-shot with no possibilities of sequels - if I ever leave them/find another publisher, they'll still own my series and I can't use it anymore. Not to mention executive meddling messing up my ideas and vision for the series... I'm way too attached to my own ideas and characters for that, which is why I won't do that and my only option for my own ideas is to go indie (or making sure I still have full ownership over the series) haha.