How can they? They don't know what it is. They are complaining about it a lot of times you don't hear about it; every time they have to fill an abomination of a form, every time they hard-close their browser because it's stuck, every time they just wait for a page to load, every time 'something' happens they did not ask for but it happened anyway.
Anecdotally, but I am sure this resonates with people who sometimes do not order only from Amazon, I tried to order some impossible meat from a site here and when it was time to pay, there was a JS undefined error and it emptied my shopping cart. This happens a billion times a day all over the place.
You just summed up the entire web development ecosystem in general. There's also the trendchasing and continual churn of breaking things that used to work just fine, replacing them with even more inefficient and complex solutions. In the area of the software industry that I work in, doing things that way would quickly make customers disappear.
The "inelegance" or otherwise "lack of purity" of JS doesn't really bother me; a lot of languages have parts like that, and I've written some JS myself.