once upon a time, when routers ran at significantly less
than wire-speed, people trying to build fast "packet
flangers" wanted a term to differentiate their go-fast
box from the "legacy" go-slow boxes.
as Vern pointed out, that distinction is now specious, at best
(a most charitable description)
i submit the continuing popularity of the term "switch" is
mostly linguistic.
"router" has two syllables and at least two pronunciations
as well as carrying some emotional stygma from the above-
mentioned exercise in new-speak.
"switch" is easier to say and is subconsciously euphoneous
with "speed" (at least in English - the lingua franca of
marketing blather), so people still like "switch"
how's that for pointless speculation?
-mo