Why would a thief who successfully garroted someone stop when they're unconscious? Why wouldn't they just continue to choke them out until they were dead? This skill seems more suited to the assassin class, and would provide assassins with a unique method for killing someone who didn't have a vuln to abuse on assassinate.

And if you think about it, thieves in general, just based on a typical perspective of sneaking, devious mofos who primarily want to rob people blind, would use stealth and brute force or finesse (see: blackjack, weapon blackjack, knockout poison, etc) but in a manner that typically isn't intended to kill.

gar⋅rote   [guh-roht, -rot] Show IPA noun, verb, -rot⋅ed, -rot⋅ing.
–noun
1. a method of capital punishment of Spanish origin in which an iron collar is tightened around a condemned person's neck until death occurs by strangulation or by injury to the spinal column at the base of the brain.
2. the collarlike instrument used for this method of execution.
3. strangulation or throttling, esp. in the course of a robbery.
4. an instrument, usually a cord or wire with handles attached at the ends, used for strangling a victim.

It seems #3 is about the only rationale for the way the system is set up for thieves in CF. Maybe it's a game balance thing or whatever, I just never saw the garrote as a passive approach to robbing someone. It's an assassins tool.