Dumb question: What are cards better than, say, a 1080ti for? Are they just stupid expensive so they aren't even considered "gamers" or are they used to process like massive matrix/algorithms and, therefore, the tech isn't especially useful for gaming?
The latter is mostly correct.
The "Titan" for example is still somewhat marketed as a "gamer" card, but NVIDIA technically classifies it as a "Deep Learning" card.
Essentially, you can buy a titan and get a bit more gaming performance out of it, but at that point you're burning money...but hey, some people have money to spend and just the one hobby to spend it on, so what the heck?
Personally, I've always been a ~$600-$700 (CAD) graphics card kind of guy. In 2011, that bought me a GTX 590. In 2015, a 980 Ti. In 2017, a 1080. In 2018/19, it'd probably get me an 1170.