From my freshman years around 2005, I vaguely remember that multi-thread GUI apps were:

- a way to avoid blocking the UI,

- tool to gain some perf. on new fancy multi-core processors,

- making the code much harder to read and debug, which often makes them a victim in a cost-benefit analysis.

I learned about it in 1991.

As a freshman CS student? Granted things were changing rapidly in the 90s, but this wasn't the case my freshman year a couple of years prior. I know that I was aware of the concept of threading by my sophomore or junior year, and by the time I graduated had encountered them first hand. I'm not sure we even covered multitasking (fork() and friends) at all in my freshman year, but of that I'm far less certain.