Not a huge amount of people will make custom styles, but they can be shared on sites like userscripts.org, for people who wouldn't bother making them or don't k

Not a huge amount of people will make custom styles, but they can be shared on sites like userscripts.org, for people who wouldn't bother making them or don't know css to use. Knowledge of basic HTML and CSS is more widespread than you might think. If you're using inline styles, you're likely to end up with a lot of elements that don't have classes or ids to target for styling, so userstylers will have to use complex selectors using :nth-of-type and such, which is harder, more fragile, and not even always possible. And every line of the userstylesheet will need !important annotations, which makes composing multiple userstylesheet on the same page more likely to break.