DS gets dunked in the bath every night but almost never has soap added. His hair is washed once every week to 10 days, depending on how hot it is and how much his head has sweated. He doesn't smell.
I have a bath once a week and wash other bits as necessary. I don't shower, I don't like it (except at the swimming pool). My hair can't stand being washed more than once a week or it descends into straw-like frizziness. I also don't use soap in the bath, just salt. I don't smell either - and believe me, if I did, my DH would have no compunction in telling me.
When I was pregnant, I didn't wash my hair for the last 8 weeks and it wasn't greasy at all - it was incredible! Didn't smell, wasn't greasy, didn't look straggly or anything - no one knew. Hormones have a lot to answer for but so does "conditioning" - as in your body gets used to how often you wash it and needs you to continue doing so.
Soap and lotions all mess with the natural balance of the skin as well. Mine is lovely and soft, not dry at all, because I don't use the chemicals.
I do use soap on my hands when they're dirty from gardening or oily or whatever - and it dries the skin out something terrible.