This is (was) largely a problem caused by holes in the web platform. Historically it was incredibly hard (if not impossible) to style or otherwise extend the behavior of a true <select>, so most apps had to reimplement it (poorly). <selectmenu> seems to be the new styleable built-in replacement.

And then because code sharing across apps/frameworks/companies/etc was historically very hard, only really big companies had enough headcount to build fully functional, accessible, customizable replacements for built-in components. Web Components solve this, allowing global collaboration on common leaf node components like <select>.

Related: https://blogs.windows.com/msedgedev/2022/05/05/styling-selec...