Depends on the game. Quick-paced, short-lived games like arena fps and rts games naturally develop large enough communities (or die trying) that AI-development

Depends on the game. Quick-paced, short-lived games like arena fps and rts games naturally develop large enough communities (or die trying) that AI-development can be brushed off in favor of letting the players deal with it. But for games like grand strategies (eg civ), the player population doesn't typically run high enough to support only humans each match (at least partially because the games run too long), and so its more important to develop a decently sane AI.