A commenter suggested I answer this question, which is similar to one I was asked after the talk.
It's true that playing online makes a lot of sense for a professional poker player. You can play from home, you can play way more games per hour, and you can keep track of very useful data on yourself and your opponents much more easily than in the casino. Although the competition is tougher (or so I have heard and believe), if you can beat the games online, it makes way more financial sense to play online than in a casino. If you get good enough at multitabling shorthanded games to win even 25 cents per hand, you can earn more per hour than someone playing live and winning $4 per hand. In addition, it's likely that the ratio of your win rate to your volatility will be relatively low because every $X that you win will come over many more hands, evening out the wins and losses. So, why didn't I play online?
There are three main reasons. All of them have to do with focusing on abstract issues related to my quality of life as opposed to my finances.
First of all, I simply don't enjoy playing online and playing in a casino remains fun. I just prefer being around people to sitting in my house at my computer. I like the structure of going out and avoiding the distractions of being at home. I like the culture of live poker, playing with real cards and real chips. I also like the aspects of pure poker that get obscured by online play, which is actually my next point.
The second reason is that online poker isn't real poker, but merely a good substitute. I want to be able to look at and talk to my opponents. I actually think this is a minor aspect of real poker, but it still matters and it still makes the game more fun and interesting. Perhaps most importantly, I think live poker is more "pure" because there is probably less cheating. It's way too easy to collude in online poker ("hey, I've got pocket aces, can you raise for me now?"). Being able to see your opponents not only makes it harder for them to cheat but also makes them less likely to want to cheat. Several people have admitted to me that they have colluded online. I doubt most of these people would be willing to cheat people in live poker because it just feels so much meaner to cheat a real person than an avatar. All of this is ignoring the "superuser" problem of poker site employees helping their friends cheat by revealing opponents' hands. (Online poker scandals listed here.) We also have the issue of poker bots, which are probably beatable but certainly diminish the "purity" of the game.
Third, it simply didn't seem worth getting back into online poker after the UIGEA was passed, which was a year after I moved to Vegas. I actually did try to deposit money once or twice since then, but when I realized it would be a complicated process I gave up and never looked back. I also try to be lawful whenever possible (I'm one of the few pro poker players who makes an effort to report his earnings to the IRS accurately and I don't attend obviously illegal home games), so avoiding online poker lets me sidestep the ambiguous legal standing of online poker in America nowadays.
So, basically I had a strong personal preference for live poker, cheating seems more rampant online, and the laws make things complicated.