It depends. If it's the Boca Raton resort with their wonderful and dreadfully-expensive peach-scented shampoo, yes. If it's mundane stuff, I take the unused portion home (the soap fits nicely in the foil packet from the coffeemaker!).
I've stayed in places where the maid threw out once-used tpoiletries every day and I've hidden the used stuff and re-used it since it seemed so wasteful.
At home, the shampoo is nice for travel when I don't like the local shampoo, or for the health club. The soap is nice to use as hand soap in the bathrooms.