steam groups

I'm kind of new to the site but am I missing something with these? You're essentially paying to be in them and there is still no guarantee of winning. Seems like you're buying games so you can win other games, wouldn't it be simpler to cut out the middle man and buy the game you want in the first place?

To clarify: you don't pay to enter the giveaway but most groups require you to do a giveaway each month (this is the pay part).