If folks had actually been using, say, the Plus and Alt classes from semigroupoids or the like more or less at all pretty much anywhere, I could maybe argue towards bringing them up towards base, but I've seen almost zero adoption of the ideas over multiple years -- and these represent yet _another_ point in the design space where we talk about semigroupal and monoidal structures where f is a Functor instead. =/
FWIW, very rarely do I write a package without semigroups and/or semigroupoids; sometimes for "not very important" or superficial reasons, but more typically otherwise. Even something as disparate as a CASR61.345 compliant pilot logbook uses both packages heavily, and for good reason (it says/implies so in the law!). Why others chooses to forgo the advantages is beyond me. Just a data point, cheerio!