xserver running as root

The xserver (or Xwrapper) is suid root.
This is necessary to access certain privileged devices.

Now I have heard that, in conformance with good security
practices, the xserver quickly gives up its root privileges
as soon as it has opened those devices, by changing the
effective user back to the real user. However, when I run a
"ps -eo euser,ruser,cmd" the effective user still appears
to be root. Is this required behaviour? Is it not possible
to run the xserver as an ordinary user (under Linux)?

Cheers.
Aurelio.