Awhile ago I read a blog post by someone who had stuck to an uberman schedule longer than most. From what I remember social pressure was part of the reason he stopped but more than that it was just very inflexible. Missing a nap would throw off his sleep schedule so he had to plan all his activities around napping every ~3.5 hours. That made it difficult to be spontaneous and any unexpected things that came up could end up having an outsized impact. Might be less of an issue with other polyphasic sleep schedules though, uberman seems like a bit of an extreme.

For me with bi-phasic it was exactly that; my family. The only way I could make it work was to sacrifice something at work or dinner time. Neither was doable for me.