Those little bottles of shampoo, conditioner and body wash in hotels—icons of travel—are disappearing, replaced by bulk dispensers mounted on shower walls. And some travelers are in a lather.

Marriott is switching to larger bottles in wall-mounted racks in 450 hotels at five brands and plans to expand to 1,500 hotels in North America by January. InterContinental Hotels Group is rolling out wall-mounted bulk dispensers at four brands this year. IHG’s upscale Kimpton brand already uses big bottles in showers.

Even...