A lot of players look for a free poker site when they first start to play poker online.
It is probably a combination of things that have them looking for free poker sites.  The natural caution when it comes to putting your money online is probably the major reason for wanting to play free poker first.
And [...]

After the early stages of any big poker tournament, when the play, and the players, have settled down somewhat, begins the long, tedious and drawn out process of crawling your way to the money.
The bigger the field the longer this middle period will be.
By this stage many of the lesser skilled players will have been [...]