Washing baby bottles after every usage!

Oh gosh! Who here only rinse baby bottle (aft milk) with hot water? Pls enlighten me! I touched my baby’s bottle & it’s oily!!! Asked my hubby and he said that his mom says that we don’t have to always wash bottle with baby bottle dishwasher soap... I’m mind-blown. Feel like rebutting, “Do you not wash your greasy plates after eating?”... sigh!