May is not programming, and math is often handwritten, so there is a lot of friction in setting up a DCVS for "scratch work". Polymath was rather awkward, and I would guess it was either (a) an easy problem for the (genius) solvers, relative to regular work, and (b) an annoying data transfer.

But here are certainly room for improvement above Blog Comments as a collaboration UI. Even a google spreadsheet would have been better.