Half the satisfaction of winning a game is the actual ending of the game. In a game like command and conquer, company of heroes, starcraft, dawn of war - whatever - when you finally overpowered your enemy, the victory satisfaction (and victors 'right' if you will) was the then destroying of the base. It was sort of the nail in the coffin and ultimate conclusion. When someone bails, it's just poor sportsmanship, rude and takes away most of the satisfaction of victory to the better player because the loser was an immature little twat.
The only problem with demigod is that if it's pretty obvious one team is going to outright win, it can take a _long_ time for the game to end. You can totally wipe the floor with the other team and if they continue to defend/fight back they will still likely lose, but will prolong the actual end a huge amount.
If anything, IMO, there needs to be a concede option that doesnt outright end the game, but either way soups up the winning teams powers/stats or way weakens the enemy structures - so the game can be concluded within minutes rather than 10s of minutes.
2c
*edit -if it's early to mid game and someone on my team ragequits, I'll bail also. I refuse to play with an ai teammate. Likewise, if someone on the other team bails i'm not overly inclined to stick around either as an ai will never ever be able to match a player in skill, no matter what kind of work they do on them. Ai is for single player plebs, NOT multiplayer players looking for actual competition.