Most of the time when I get a game for free I don't value it as much. There are some exceptions, I've gotten into a few giveaways like Dead Island 2 and Lord of the Rings Return to Moria.
But mostly I want gaming to be convenient. Steam is very convenient and has some really great sales. I recently found a space tower defense game I wanted to try and it was 0.79 on sale. Less than a dollar.