Which kind of freedom do you need ?
I'm sorry, i never answered that

There are some custom software packages installed on a server that hosts a good community.
For instance sphinx indexing server, spell checker software and i am experimenting with gnubg output (long term project, just for fun

).
So i would need root access to install these packages and they don't give root access in free (or cheap) hosting accounts. (check it out).
Also the amount of emails that is send via the system is large and still growing. It sends hundreds of emails a day. Free hosting (or cheap hosting accounts) don't allow you to send that much emails (or any email).
There are more reasons like: security, cronjobs, backups, etc. etc.