> assuming the user is an expert at it, rather than the author of the document
But the user is NOT an expert at styling a website, this is why we have designers to figure out which combination of layout, fonts, and colors work well together.
Users generally don't give a shit about styling as much as UX designers justifying thier salaries. There are probably more people who suffer daily from accessibility on the web than UX designers in total
Well, they will make styles that are slow and/or that many users do not like. Instead, let it be subject to the user configuration; the web browser designer can put in suitable default settings.
But the user is NOT an expert at styling a website, this is why we have designers to figure out which combination of layout, fonts, and colors work well together.