Using DHCP for a server is perfectly fine for quite a number of networks. You simply make a DHCP reservation so it gets the same IP every time it boots. Granted, there are not many reasons to do it this way, but it is perfectly valid and works fine. Using DHCP doesn't reduce a server's reliability at all. My network is set with DHCP reservations so that if I decide to change something, I just change the reservation and remotely renew the address. I use this for company workstations regularly and it works quite well.