The case in question is that of one Tyler McCandless. He's clearly a brilliant guy, you don't get degrees from Penn State as well as a PhD in sciences if you're a dummy. And sure, right out of college he could have had a Mizuno deal that got him travel and gear plus a modest stipend which represented an outlay of more than 10, 15 or 25% of his annual income. At this point, though, it's a tough sell. He's slipped from Mizuno to Brooks (iD?) to Newton to Altra/Rabbit.
No problem at all with having a gear deal, get whatever you can from the open market and it's good that companies still see value in his performance and image. It's not that anyone's saying "oh he acts like a pro runner" because he has slim sponsorship deals, he goes around telling people that he's a pro runner:
He's a damn good runner, better than almost all on this board are or ever were. It seems rather disingenuous, in the way that strippers claim to "only be doing it to pay for law school." Just take his most recent race, a half in Florida where he won by a minute yet while avoiding the competition in Houston on the same weekend. Maybe the Florida race offered a better appearance package than Houston would offer to the runner-up at US marathon champs two years ago. He plays the SM game really well, his loves to talk about himself and his selfies are on point, gotta give him that.