I'm presuming the conditional moves are used in long chess, that is 1 day per move or longer, rather than classical chess or blitz. In short chess, they use premoves instead. It's basically the same except it has more strategic value, especially if both players are under extreme time pressure. Throwing a random "bad" premove in can often be met with a premove that anticipated a different move, and can result in a huge blunder.

I don't really like fast chess. I want to play the highest quality game I can, and that happens with proper deep analysis instead of quickfire mental calculation.