[Spktyr]

Nope, there are plenty of classes and competitions where DA is permitted, and they usually end up losing.

[Joe 6-pack]

In IPSC and PPC classes the disadvantage of a DA/SA is that they are required to fire the first round in DA mode, even if capable of firing SA. Converting them to SAO overcomes this rule.

I do believe under older IPSC rules, some classes excluded DA pistols altogether.

In the real world, where one may carry a DA pistol prepared to fire the first round SA if desired, those rules do not apply.