I did have clean underwear every day as a child, but baths/hair-washing were weekly (until I was a teenager and would have baths just for the pleasure of it!).
My main concern regarding the immunity of today's youngsters is the possible effect of over-exposure to antibacterial products. People seem to be spraying them all over their homes without any thought.
There are good bacteria as well as bad, and what might the consequences to our bodies be if a)we kill the good bacteria or b) upset the balance of bacteria in our guts that our bodies have evolved to need?
The adverts for washing detergents with antibacterial in them make me furious. I honestly think that in the long run it could turn out to be far more harmful for a young child to suck clothing / bedding that's got antibacterial products in it than, say, to suck a dummy that's been dropped on the average floor several times!