It's called selling out and it's socially accepted because it's a survival necessity for nearly everyone. There are principled communities where it matters, and then on the other side there are websites like this one dedicated to the idea of selling out. For everyone else their prepackaged rationalization is the Yuppie Nuremberg defense.
There are principled communities where it matters
If you have a few examples of these I'd be very, very much obliged.
The Death Metal scene has pretty much no sell outs. There are a few examples, but it is definitely a community where selling out is the worst thing you can do.
I'm not talking about a hippie commune or something, but that in some subcultures it is actually a thing people mentally struggle with and make decisions with more emphasis on principal than money. Another commenter gave the example of death metal, which is a good one because music and art in general are where I see the attitudes the most.
Selling your soul is bad business, you want to rent it out so at the Oscars you can still rail against the man.
... while taking a Samsung-sponsored selfie with the man.
Exactly.
Well I guess technically, you also rent your body, since you can't legally sell yourself into slavery.