Is it necessary to raise humidity for shed?

[Slim]

However, I try to have the humidity on the low side where I can to inhibit growth of nasties to make cleaning easier.

as Raven pointed out, it does inhibit the growth of nasties (NIH recommends staying below 50% since mold will readily grow above that)

Using an Iris Sweater Box, kraft paper substrate, two RBI hides and a crock water dish, I've never had any issue with these nasties of which you speak. I hold 65% on a pretty consistent basis, but never grow anything in the tub except snakes