Addintionally, basing it on pe'a brings up another confounding factor.
Sometimes, the technical sense of a word *is* also metaphorical. It'd be
confusing for something to be both pe'a and pe'ainai

Take this hypothetical situation; we are Lojbanist scientists back in the
1960's, working on this newfangled machine called a "computer", and we just
invented the "computer mouse".

We could call it (smacu pe'a); but the problem is that (pe'a) is inherently
fuzzy; we can't assign any one meaning to it, even within the very narrow
context of being inventors of a bleeding-edge technology that we have no
idea of its future potential.

However, we can assign a meaning to (zai'e smacu) within this particular
narrow context of computer science. We don't even need the (pe'a), because
by assigning it the jargon meaning, we have divorced it from its original
meaning. We also don't care if anyone else assigns a meaning to (zai'e
smacu) while working on something completely different; all we care about
is that within this particular field, we have assigned one meaning to it.

Then fast forward a few decades. Computers become a very big thing, and
have gained mainstream acceptance. We've even added the gismu skami to
the dictionary. Thus, laypeople have a need to talk about computer mice.
Thus, they can take (zai'e smacu), turn it to (zamsmacu), then add the
rafsi for skami, making (samyzamsmacu). Then after some amount of
high-frequency usage, they may just drop the -zam- rafsi altogether, making
(samsmacu).