I tend to think that sci fi movies and shows and anime put tons of stuff at Lagrange points, but when I stop to think about that it's really just that I assume Gundam Wing did it because it was a trope, which is not necessarily the case.

I associate them primarily with the habitable gas torus of Larry Niven's The Integral Trees (1984) and The Smoke Ring (1987), which I adored in seventh grade, also the covers by Michael Whelan.

I hadn't heard of Planetes at all, but when I sketched the setting of Space Sweepers to rushthatspeaks, he mentioned it at once.