Lattices (the algebraic structure) seem to exist only on Wikipedia in the sense that the only time I've seen lattices every mentioned in my standard undergrad education is once for a proof of the Stone-Weierstrauss theorem.
I know there are textbooks on the topic, and probably lots of people who deal with lattices a lot. But my own experience seems to be that wikipedia puts more emphasis on lattices and things like universal algebra than actually happens in math.
There is an interesting rant from Gian-Carlo Rota on why lattices are so rarely taught despite being so ubiquitous. I include them based on the amount of use I have gotten out of them over the years. For example, the entire theoretical structure of eventual consistency is "make your merge operation the meet of a semilattice."
I know there are textbooks on the topic, and probably lots of people who deal with lattices a lot. But my own experience seems to be that wikipedia puts more emphasis on lattices and things like universal algebra than actually happens in math.