And that reason is....
Simple... every router... no matter how close to perfect.. gets locked up every once in a short/long while.
My netgear had web access directly to a restart page (only from the LAN side). I ran a cron job that checked once an hour, and if it couldn't get out.. it restarted the router... that particular "gem" of a router needed to be restarted every few days (it had an overheating issue as best as I could tell).
The DIR-655 is MUCH more stable.. but its not perfect. I had no internet ~2 weeks ago. Unplugged the router and replugged and I had internet again... if it had had a restart, I could have done the restart automatically instead of having my internet down for several hours (it died in the middle of the night).
So yes, a restart feature would be welcome.