I agree many people utterly fail, because I think that's largely because the past-time itself attracts those who have difficulties with addiction, time-management, and social interaction.
You list some things that make it really hard to live a normal life, but I disagree with some can offer counter-points to others.
You say there is little interaction with other people. This is true for many but doesn't have to be the case. I spend a lot of 'work time' talking with like-minded professionals, studying together or just daily banter. I probably have more social interaction through work than the time I worked in a small development company, and certainly more during my periods of (failing to) run startups.
You say working hours are partially out of your control, but with most forms of poker you can work any time of the day (literally any time in 24 hours, 7 days a week) - some times may be better than others, depending on the game you play. There's a lot to be done away from the table if the games are quiet. Compare this to the lack of flexibility with any other job: either a rigid 9-5, or at least restrictions on when business is to be done (conference calls, deadlines).
It can be stressful and tiring, but listening to some start-up stories here on HN, it can hardly compare! Some of you guys are working yourselves to death! Certainly you can put in long hours in poker, but it's a daily choice. The more hours at the table, the more money. I also believe that poker is actually fairly low-variance compared to other jobs, such as a running a start-up: Long days with long nights, hacking at weekends, all for a very high risk of failure months or even years down the line. With poker you can't count on a weekly (or even monthly) pay-check but in the long term, you cash in with regularity
Personally I like to work around 3 hours a day, 7 days a week. I might put in a short morning session, and a short evening session. Doing this it feels like I have all the day off to spend socialising, hacking on some pet project, relaxing. You don't have to hit the high-stakes to make a living from poker. In the "5-hour-work-week" concept of salary you earn very high, because I have no commute and flexibility to live anywhere in the world. I have moved continent 3 times in the last 3 years. I can jump on a plane and visit friends anywhere, and as long as I have an internet connection I know I can be there, on holiday and making money at the same time. And if you manage your time correctly, you should have time to fully develop other projects, be they startup ideas, or just other, more life-fulfilling hobbies.
There are certainly negatives to the job, but - at least to me - there's an overwhelming number of positives that many (including a lot of professionals) just don't focus on. If you take advantage of what the job has to offer there's no reason it should be the lonely, frustrating grind that many feel; quite the contrary.