Not totally understanding the question here.
2 Questions come to mind that would fit your post:
- Why do they not host a full client with their changes already in place for a download with a custom install program?
- Why do they not host a custom Classic/Kunark/Velious only client with a custom install program and current updates for this server?
- Why do we not support the original Classic disk that was brought out when the game first became live?
If your questions center around the first 2, then the simple answer to this is they legally cannot do this. They can only legally run the game on their custom server code, allow connections from Everquest client, and make changes here and there but hosting the client in any way could allow SOE to target the project even though they do not make any profit.
Now if your question is actually the 3rd one, then the reason is they have used the Titanium client since the start of the project I believe because it holds both Kunark and Velious expantions and it is also the easiest to get ahold of.
The Team
{as far as I know} did not want to have to support more than 1 client at a time.