True, Maison Ikkoku's popularity in North America is lower than certain other Takahashi works or a franchise like Sailor Moon. At the same time, VIZ has kept Maison Ikkoku circulating in both print and video formats, since the early 1990s; the final DVD box set was released in 2006, and this most recent manga version is the series' fourth North American edition, when counting the 30-or-so page floppies. Price and format-licensing issues would potentially be a more likely reason for the lack of a domestic Blu-ray. The two, initial Japanese BD sets for the TV series were released in late 2013 & early 2014 and (using quick-and-dirty math) were roughly $385 each; a single, priced-down set was made available in 2017 for roughly $365. VIZ would probably be willing to do a multipart set, but obviously nowhere near the Japanese prices. We're now at a point, where all those Japanese sets are--if not out-of-print--largely unavailable, which should increase the ability to obtain more reasonable N.A. licensing. None of this means, of course, we'll see a domestic BD set, but VIZ's current video release schedule is fairly light and they're again pushing the manga.
As for Urusei Yatsura, in truth, I'm not all that bullish on the prospects of the television show becoming available again in the U.S., but with Discotek's previous BD for UY: Beautiful Dreamer and forthcoming releases of the rest of the movies, it's the first instance in some time since customers in the U.S. had the ability to demonstrate support for the series. Urusei Yatsura in anime form probably doesn't fit well in the portfolios of most North American anime distributors, making the movies' performance one of the few indicators for the TV show's viability.