Actually, guys often use hair conditioner in the shower. I know my husband has used it to jerk off.
It also feels very good when we are both in the shower and he is rubbing his hands all over my body.
Conditioner is also a great anal lube for enemas and colon tube insertions.
I do not think I would enjoy shampoo in my vagina.
For rectal/anal lube for an enema, it could be fine, but watch out because some shampoos, especially dandruff shampoos can be extremely caustic and painful on rectal mucosa.