But if you talk about professional poker players, they can make a living out of it as well as long-time sportsbettors.
Professional poker players also have a lot of other sources of income. Many of them are doing stuff like:
-writing a book on gambling or poker
-doing affiliate marketing on their website for a casino
-giving out premium picks on membership channels
-building their own casino and running that
We should not narrow down their sources of income as poker or sports betting as said. There is the this "cushion" of income to back them up and all these are the non-gambling modes of earning.