Interesting article, although it kinda reinforces a false dichotomy - just because this player had an unhealthy lifestyle playing poker, doesn't mean you can't play poker professionally while living a perfectly healthy and otherwise normal life. In fact, the article keeps mentioning the "lavish" lifestyle of the poker players as a given, when that is also just a choice they make. I've always enjoyed playing poker. I'…
My theories as to why would be too long for this forum, but the two big ones are the losing streaks and lack of respect for money.
Losing streaks are like nothing you can understand until you've been a professional poker player. Imagine if you went to work, performed flawlessly, far better than all of your coworkers, and instead of getting paid your bank account got debited and your boss told you "you really sucked today". Then that happens every day for a month.
Humans (and especially poker players, who study probabilistic decision making as a hobby) are conditioned through life to believe outcomes are a direct result of actions. Do a good job at something and work hard at it, you succeed. Do a bad job at something and slack off, you fail.
While this is true in poker in the long run, the long run can be a long time. I broke even for a year at one point, and that's at cash games. Meanwhile donkeys without the slightest clue what they were doing were lucking ass backward into multimillion-dollar tournament prizes.
You can't even fathom what this does to you emotionally until you've lived through it. It engenders self-doubt, which gets you off your game, which probably makes you play worse, which you know you're doing but aren't sure exactly how, or what to do about it, which in turn prolongs the losing streak. There is no end to it.
The lack of respect for money is universal in a world where thousands of dollars change hands in minutes. It's impossible to think "I shouldn't buy that Lexus I've had my eye on" when you just made enough to do it in the last 4 hours. Everytime I played a pot I was risking far more than I was playing credit card roulette for dinner for 4 at Craftsteak. (BTW, my luck at credit card roulette is legendary. If my luck at poker had been half that good I'd have won the WSOP.)