I find it pretty crazy. The chance to make quads when you hold a pocket pair is about 0.86% but I'm making on average 2 quads per day, I don't know how many played hands that is but in the range of 1500-4000, and not just with pockets, even with one card.
I've also seen two guys from my community commenting about how often they get quads and one of them even made a screenshot with all of them. The problem is that I don't feel lucky at all, since I see them at everyone and occasionally lost some big pots, once with AA with three K's down because opponent had K3.
On the other sites I've played quads weren't common at all. I barely made several in 200k hands so I'm normally not counting this possibility, however given recent history maybe I should

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