You mentioned a used model that is over 5 years old as an example of "a new computer", and "1k" as "not expensive for consumers". It is honestly impressive how well you undermined your own point.
> If enough consumers aren't able to use the website, then business wouldn't use it.
I sincerely doubt any business owner would approve of losing even 10% of their potential users/customers if they knew that was the trade-off for their web developer choosing to use this feature, but there are disconnects in communication about these kinds of things -- if the web developer even knows about compatibility issues themselves, which you would expect from any competent web developer, but there are a whole lot of incompetent web developers in the wild who won't even think about things like this.
Most web devs get screemed at (by their peer reviewers or [preferably] static analysis tools) if they use a feature which has less then like 98% support without gracefully denigrating it, and rightfully so.
But your GP is in a massive minority, if every developer would cater to 11 year old browsers we would be wasting a lot of developer time to inferior designs, with more hacks which brake the web for even more users.