I think the main point, is that to most players it doesn't really matter to them what server side software you are using, all they care about is the rules, how it's run, and what the gameplay is like, and whether they need to install mods.
The main 2 reasons why advertising is banned site-wide, is:
- SpongePowered have advertising deals to help keep the site alive / online.
- Specifically with a server list: it's a lot of extra work to moderate, with potential to cause more drama inside the community, as well as people inviting people to the forums just to bump posts and recommend. We would rather keep the forums having a higher signal to noise ratio, in order to keep it a useful resource for server admins / plugin developers.