Does "Demand Surrender" ever work?

[resonantblue]

I've had a city surrender to me after a random straggling army outside the city attacked me, which drew out the garrison, which I crushed.

The garrison left in the city was tiny compared to my besieging force and they surrendered. As someone pointed out, it was kind of a waste since they were expelled rather than destroyed and went on to raid towns/etc in the region.

The one place i can see this being useful is if you really don't want to have to manually assasult the fortress (even with a small garrison in it) but don't feel like losing 1/3rd of your stack on autoresolve, which seems to give yo uenormous casualties regardless of how small the garrison inside is AND you don't feel like waiting for the siege to force their surrender.