In EU most of the countries has bad internet over ASDL, so limiting upload and download speed while syncing files is important, because to big upload can kill whole home network download and vice versa. For example on speed asdl like I have I can upload 2000Kb/s but without limit it can go up to 2300kb/s which kills my internet connection. So I can only use cloud disks which had these limiters build in. For example, Mega, Dropbox, OneDrive and Tresorit has it, but not proton.