My cynical take: Because Reddit didn't pay like a FAANG to begin with.
(I don't actually know if this is the case though, I've never looked into employment with Reddit)
"Because we learned that their impact isn't differentiated based on their location, we knew that we didn't have to pay them differently within the US, so we eliminated geographical zones from our compensation structure and now all employees in the US are paid within the same range and it means being rewarded for their impact, not their location."