A legitimate attempt to respond to the question:
(a) It's not "wrong" to play bass with a pick.
(b) But most people that I see play with a pick, only play with a pick. Playing bass with a pick certainly gives a very distinct sound, one that is desirable in some situations. But not all.
In the past few years, I've got a few young folks started on bass. I'm not a guitar teacher at all, but I always tell them to wait for a while before they begin to experiment with a pick. Otherwise, they'll start using a pick and never stop... cause yeah, it's a little easier on the fingers.
So the answer is... playing bass with a pick might become a "crutch" for some people. That doesn't mean that every bass player needs to avoid it, only that it they should learn to use it when the song or situation calls for it. Certainly you might be in a very specific band where you want that sound all the time... like Dee Dee.