Have you actually tried washing one? I initially thought the same, so I chucked my first screen protector without trying, but then I thought, what have I got to lose, when the next one got some dust on it, I tried giving it a soapy wash, a rinse to remove the soap, shook off the excess water and it applied just fine. And they were the cheap ones as well.

Also I tried running a hot shower and doing it in the bathroom like you suggest, it didn't help the problem with stray dust particles for me.