dither is sometimes used as a technique in the design of digital hardware
Indeed it is ....but our ears behave in a classic digital pattern. Tiny hair movements trigger nerve bundles that send "digital" signals to the brain. Once a nerve bundle fires off - it takes time to "reset" so it can fire again. Certain forms of dither may indeed have an impact on what we hear....our ability to hear beat frequencies that are not actually there is perhaps a product of this strange digital ear phenomenon. I think part of the way reverb works so well is that the multiple later arrivals give our ears/brain more time to analyze each instrument/sound.