Wow, that's a good point. But when I play the Japanese version running isn't always as quick and guaranteed. Try running from a Behemoth or Death Mask. Perhaps that's what they were designed for?
Trivia, I use Smoke as an experiment to test different effects. Never liked that spell.
Something also occurred to me, using Exit or Smoke doesn't have the party lose GP.
That's only because of Speed, I'd imagine...
I just tested running from a Boss Bit Imp and the same instant run occurred.
Now let's see what happens when I set an EvilMask...
No issue, Speed lets one action occur before the player can run. But that's it basically. I tested this by setting the Speed of an EvilMask down to 1-3 and the run was immediate.
I imagine the same will follow with Behemoth...
No problem running from a Behemoth. It's quite likely you may have imagined that running wasn't as quick because enemy's had a decent enough Speed to attack you as soon as the battle began instead of several seconds afterwards.
Yes, the only purpose of Exit and Smoke are to avoid losing GP. Hence why they're some of the first spells I get rid of (once an actual run statistic is put into the game, that will no longer be an issue)