Don't listen to Gaylord and the other squeaky old grandma's. It's merely an old joke. Like kidding English about their famous lack of dental care.
English and Europeans have a reputation of not taking the twice daily showers that a lot of American's have become addicted to.
I have an English friend that thinks it's crazy that Americans can take two showers a day. Even one a day he thinks is not necessary.
The "once a week, whether you need it or not." is just an old phrase that may not translate well to some who is not a native speaker. Sort of a running cultural joke.
This place has been taken over by old women with menstrual ailments. 
Well, there's some truth to it. Bathing in the sauna on Saturdays used to be the norm during winters especially on the countryside, a can of water and a vat beside the bed for washing your eyes in the morning. There often was a large cauldron in the cattle shed as well where you could wipe yourself with warm water after all the milk bails and churns had been washed. In the summertime swimming was one way to take care of personal hygiene in the "Land of a thousand Lakes" - actually over 180000 of them. - There's a favourite song about lumberjacks who turn their shirts inside out on Saturdays when they go to a dance.
I guess it was pretty similar all over the world until the mid 1900's. City people had had showers and plumbing already in Ancient Greece and Ancient Romans continued the tradition but I bet the farmer living a day's walk from the town didn't use such luxuries too often.
Funny that although shower is actually a British invention it's the Americans who have taken taking a shower to another level. Then again, I haven't heard about landslides caused by collapsing groundwater cavities in Europe.
Finally, to show that Americans may also have their blind spots in hygiene: There was this middle-aged couple in an old fancy hotel in Paris, France. The hotel maid showed them all around the suite and the lady was all aah's and ooh's. Finally they came to the bathroom with all luxuries including a bidet bowl. And the lady asks 'Ooh such a pretty tiny tub! Is that for washing babies in?' -'Non, Madame, it is forr washing les bébés
out!'
