the cabin needs humidity. that's why you have the frost on the inside.
Nasa, Esa call me out if i am wrong. there are two good reasons to have humidity in spacecraft. human comfort and prevention of static charge buildup.
without some humidity in the craft, theres not much else to equalize the differential electrical charges among the components. otherwise things start to arc.
i suppose, traveling through the (charged) solar winds you could encounter another spacecraft with a strong enough opposite charge of your own and if you get too close. zap. just like shuffling across a carpet. the concept art of inside a nebula did show lightening.
as for the outside, i'm surprised there isnt a mechanism of solarwind, dust and rocks sandblasting and/or pitting the windshield. the stars are constantly putting out solar wind, especially so close to them as we get to them.