It's a good question, I don't know why you're downvoted.
Because the synchronization protocol (backed by Git) is operating in the background, web frontends are always just querying local data, so it's actually quite fast. You can try browsing the linked repository and see for yourself.
and as such, it makes for a poor user experience on the web.
(when you're just downloading files over P2P, this isn't an issue or noticeable - but when you're interacting with a web site, it is)
EDIT: why the downvotes? I'm just asking a question.