Other than force powers, i've yet to find an instance in where someone does NOT USE strength (or stamina which is based on strength) to soak something, from Drugs, to diseases, to mind control devices.. Other than resisting opposed skills (con vs con, intimidate vs willpower etc), there is NOTHING that uses Per as a resistance, that is NOT force related...

But as we see in RL, someone get's hit by teargas, whether they are the 'barely 100lb soaking wet, 5ft 2 stick figure gal, or the 300lb ex linebacker, that tear gas will affect BOTH in a "PHYSICALLY similar manner", but depending on their wits and such (Perception!!) depends on how long one is affected..
Same with sonic weaponry...

So why is it no tech in SW goes against Per instead of Str??

you would think that with the large # of high strength aliens out there, the empire at least, would have developed SOME weaponry that could attack them, and NOT go against their high Str, by hitting their weak Per...