There are plenty of arguments against playing poker for a living that have nothing to do with income. I went into it with the intention of doing it for a fixed period of time as an experiment, and that's exactly what I did. I learned that I didn't really enjoy playing full-time for long periods of time, and that I was much happier working in the computer industry.
I don't have to go to work every day and deal with drunken abusive assholes. The people around me aren't pissed because they're stuck thousands of dollars. The problems I deal with are ever-changing and far more intellectually challenging than the ones I dealt with at the poker table. Choosing an office because the people around me are bright, educated, and movitavted is an advantage in a startup, but a disadvantage when selecting a poker game. My coworkers never throw punches at each other.
Poker players can be an extremely unpleasant bunch, and surrounding myself with them every day just didn't contribute positively to my overall happiness.