Yes, so the link doesn't have to be relative to the current host. If you move user posts to another server, the href changes, nothing else does.

If suddenly a bug is found that lets people iterate through users that aren't them, you can encrypt the url, but nothing else changes.

The bane of the life of backend developers is frontend developers that do dumb "URL construction" which assumes that the URL format never changes.

It's brittle and will break some time in the future.