I think this says it all....
http://deadspin.com/why-its-hard-for-poker-pros-to-make-a-living-playing-l-1526098295
The biggest problem with tournaments is when you lose, your out. If I bust out in a cash game because of a bad beat, bad decision, ect... I simply rebuy and can easily recoup the loss.
The second is clearly explained in the article. Even if you are a positive ROI player, you have to play a LOT of tournaments to really make money (enough to live off of).
I cash in micro tournaments consistently without a problem (40% ROI). But if you look at that, its not as impressive as it sounds. If I play in a 10.00 tournament, I'm going to be winning 4.00 on average (14.00 which is about a min cash). Lots of work for 4.00 and I would have to play non-stop for a month to make anything significant grinding that out (with a 40% ROI).
When I move up in games to the 100-1000 range my ROI drops to about 15%. Again, when you risk 100 to win 115, not really impressive.
I think the best thing is hope things run well in a big tournament and make a big cash rather than grinding tournaments. You will be far more profitable and consistent with cash games. I've always liked the idea of playing satellites and taking a chance on bigger tournaments rather than consistently cashing in micro tournaments.