We all used co-routines in Windows 3.1 ("co-operative multitasking"), and the application Window would go blank. Then we got threads and we were able to kick off compute to the background without having to be careful to yield throughout our background task.

For instance, of a spreadsheet computing values.

A more common use-case, however, is of trivially parallelizable problems which are completely isolated. Consider Monte-Carlo simulation for instance, where the thread hand-off to workers is done by a queue.

Making categorical statements like this political and unhelpful, and is one of the things that annoys me the most about IT culture.