If you want to get a programming job, you want a good looking CV. By contributing to prominent open source projects on github, github's popularity and fancy profile system makes it look real good on a CV.

Github is a magnet for lazy vibe coders spamming their shit everywhere to farm their CVs. On other git hosts without such a fancy profile systems, there's less on an incentive to do so. Slop to good code ratio should be lower and more managable.