PLCs for me were always that thing that "other EEs" talked about. I've never used it, though many have told me stories about ladder logic and whatever.
I recognize that the market for PLCs are huge, but I don't even know where to get started with regards to understanding them. On the other hand, I've always felt like the humble microcontroller has always done what I've wanted, so I guess I've also never had the need to reach for the PLC tool.
As EE has turned into a hobby for me (despite spending 4-years of college on it... I'm just a humble programmer in practice), I don't think I'll personally come across PLCs. Microcontrollers are king of the cheap hobbyist market for a good reason, while PLCs are found in more industrial systems and larger platforms that are likely outside a hobbyist's budget.