seeing how my beatmap folder has several GB in size transferring it to a remote server over a network would not only take a decent amount of time, it'd also skyrocket traffic as well as put up servercosts because someone has to store the amount of data you want to transfer.
With the amount of people just going inactive every day this would also mean you have a redundant set of data for a lot of people who won't even use this and the benefits of it is convenience for the amount of people who happen to own 2 or more pcs and play osu on two or more of them
and uhh tbh that's not the majority of the playerbase and it'd most likely come along with infrastructural expenses on the developing side so I don't see the urgent need nor a very valid reason as to why this should be a thing
also this is a feature request because well you're requesting a feature lol