Why is not Path of Exile at KICKSTARTER ?

I'd say the game is doing a good job of sustaining itself as-is, and Kickstarter is mainly meant for projects that need an initial round of funding. If anything, GGG should work on getting the game placed on Steam - that would increase awareness amongst a significantly larger userbase (surprisingly, none of my Steam friends actually knew about PoE, even though most play ARPGs).

$2.2 million is a pretty good haul for a game not even in open beta yet. Hopefully, the exposure to a wider audience will continue to generate enough revenue to sustain development - GGG has definitely managed to create something special.