Well i dont want ot get into the reasons, but I would guess that only about 20% of players playing online poker ever earn enough to receive a payout! The rest of the money goes to 10% of the players.
Now I have done pretty well, but it is basically because of a $12,000 first prize satellite poker tourney that I won from pokerstars. I consider myself a pretty good player, but I like to play in live games where I can see the players more than online games.
Now having said all of this, let me give you some advice! FIND one site that you like alot and play a few hundred to a few thousand hands and watch the patterns. Maybe play the small stakes tables for a while. Now I only say this because these games play MUCH differently than live poker games.
NEVER in my life have I seen so many pocket aces or pocket kings as I do when you are playing in a 2-4 person game. I mean, the software gives usually 2 people great hands. IN real life situations, unless bluffing is involved, the cards are not near as good.
Now i know that some people will say that on TV they always get great hands. WELL they dont show you the dead hands on TV!
SO learn a few things about your site. FOr example here is a big hint! If you see the first 3 cards suited on the flop, you can pretty much assume that you will see another one as well. LIkewise, they inside straights DO HIT with more frequency on the net! SO if the betting is not high, then ALWAYS make sure ot see that river card!
Some will say, why is this? Well that is because the house makes more rake on the big hands!