I play because I like the challenge of learning and playing a game where there are so many variables, not the least of which is pure luck. Managing luck is the hardest part of the game IMO.
I don't do it to "earn" money, but winning and profit are the only true indicators of success in this game. The more you "earn", the higher and more challenging the stakes that you can move up to. So "earning" is a necessary ingredient for me, but not a goal in itself.