From the other end of the spectrum there are a lot of backend engineers who don't want to touch the frontend.

IMHO aside from javascript, there's a huge tedious side to frontend engineering involving html, css, browser incompatibility and ugly hacks that aren't really programming in a sense (more just endless debugging). It's all very domain specific knowledge that doesn't translate well onto other facets of of traditional programming. Hence a lot of backend devs want to stay away from that so they build a wall of separation between the people who do want to deal with it and the ones who don't: "Frontend" and "Backend" engineers.