Or games. Or web servers. I think the author might have forgotten to suffix the title with “for the work I do”.
Games on the other hand? Oh yeah, you definitely need threads for that.
It's important to note that "multithreading" specifically means shared-memory model of parallel processing. Games are more of an exception than the rule when it comes to being well suited to shared memory.
Also, any UI app should basically be multithreaded to prevent interface hiccups.
Threading works ok, but there's rarely much shared state so the fork and pipe / she model wins cleaner and more secure.
As for UIs: maybe! I'm sure it depends, but this isn't an area I know a ton about