LinuxMCE is intended to be the center of your entire house. As such, it provides DHCP and gateway/firewall functions at its lowest level. These are used to both find devices that appear on the internal network, such as file servers, IP phones/adaptors, or other periphreals.
If you turn off our DHCP server, all of this functionality will be completely eliminated, and 90% of what you would use LinuxMCE for, would also be eliminated as a result..
Therefore, if all you need is just a media server..I think you would be happier with one of the media distributions like MythBuntu etc... because it's not worth it fighting the appliance nature of the software stack. It was designed for one major use case, and the effectiveness of the software decreses markedly the farther away you stray from this use case.
Note that I am saying this from a user's perspective, if you are a developer, or if other interested developers wish to add additional use cases for our software, we would be more than happy to accept patches for said functionality.
-Thom