If you mean by hosting it on your own computer, some people can't port forward (me, I have an airport extreme router and I use windows 10, apple doesn't let me do a single thing) or even if they could, the server quality would be terrible.
As for online server hosting, I've found that they all have time limits, low player counts, no FTP access, start-up delay/queue, and more restrictions or down-sides to their free server hosting.
However, if you're satisfied by these low-quality servers, then feel free to play through them rather than http://prohost.gs.