Breaking accessibility for looks is the cardinal sin of web development. The two are not exclusive and often it's actually less work to make things accessible — simply don't break the built in functionality. It's a widespread issue and mostly I'd put the onus on bad education: to this day, many big libraries have very poor accessibility both in their code examples and their components. The true measure of a website's user interface is not whether it's pretty, it's whether it's usable, by everyone.