If one were to wear the same pair of underwear every day without washing them, you'd probably smell bad and end up with nasty rashes. But unless you are homeles

If one were to wear the same pair of underwear every day without washing them, you'd probably smell bad and end up with nasty rashes. But unless you are homeless where it is difficult, everybody changes their underwear daily and washes it after every use. If you don't wash your plates, bowls, and utensils, you can get sick due to crud which has grown on the residual cruft. That is why people wash them between uses. If you are using your mask long enough that it is developing bacterial growths, that is your fault and isn't flaw of the mask. Wash your mask after every use, giving it ample dwell time in the soap before rinsing it. Wring it out, hang it to dry, no problems.