I think there are a couple of misunderstandings here.
One is that a guy needs to 'touch himself'. I often do not - just pull down the waste band - it's already pointed in the right direction!
Second is if I do, I'm only touching skin - much like one hand touching the other vs a female who has to wipe the much more delicate internal vulva.
That's the reason women wipe themselves toward the back - not forward. Men can easily wipe forward without the risk of contamination.
By and large I think women are much more sanitary about this than men - simply because they have to be.