More ways to talk about the priesthood

My last post got me thinking more about priesthood and terminology, particularly something Jeanne and i have been wondering about as we’ve been reading some old church history stuff:

Why don’t we use the term lesser priesthood (for what we nearly consistently call the Aaronic priesthood) anymore?

It seems a completely serviceable term, and it also seems to have been the preferred one a century and a half ago (not to mention that it has solid basis in canon), so why has it fallen out of fashion so thoroughly?