Because I think it is a new thing. People definitely did not do the amount of washing they do now. I am almost 70 and no way when I was young was my mum wearing things once and then washing them or washing the towels after one use. Nor did me and my siblings wear something once and then it was washed unless it got dirty or stained.
Also we only bathed once a week and had washes daily whereas most people today shower or bath daily so even less need to keep washing clothes after 1 or 2 wears.
Before my mum got a washing machine she washed by hand but even once she got a machine she was not always washing.
How, if you only wash things when they need it, are you doing 1 or 2 loads a day? Do you have lots of children? For me and DH I do 2 maybe 3 loads a week.
Also there was not the information about climate change and the destruction of the planet in the past. We are, or ought to be, fully aware now of the damage we are doing.
I'll take your word for people washing their clothes several times a day but considering my parents, grand parents and great grand parents were all Londoners I have never heard of that. Even if true, if their clothes smelt of smoke, I can see why they would do that. A quick google search tells me victorians didn't wash their clothes very often, in fact usually monthly.
As I said before, keep washing clothes reduces the life of them and tumble drying reduces it even more. Maybe the frequent washers also are also always buying clothes too! It is recommended that jeans should rarely be washed and some people say they should never be washed.