It at least inserts some uncertainty into the equation, and encourages seeing if you can improve that situationally.
I mean, lets get real: as I've noted before, most parts of D&D (and most games far as that goes) at best encourage engagement in the mechanics of combat; everything else gets roll-and-you're-done (when it doesn't push off things to entirely player level decisions, i.e. frequently "Do I know how to play the GM?").
But when you don't even have to bother to roll (either because its basically certain or basically impossible), that's not exactly going to increase engagement.