(speaking from experence with eq ui mods)
The biggest problem with someone else hosting your UI and you have no access to update it is that you have people going there to download the (old) version of your mod from that site, get errors, figure out how to contact you, complain that there is a problem (that you know you've fixed) and you try to fix it and then finally you find out that they're using an old version. Not to mention the frustration of the users that just download it and go "well thats a load of hooey - that remelio's stuff doesn't work worth a darn" and then never download your stuff again.
So thats the reasoning behind it. Its not that they don't want free hosting, its the headaches that arise from the fact that the game is constantly in a state of change, and new errors arise all the time from updates making old versions obsolete.
Hopefully I explained that well.
Feel free to add in anything I missed.