The thing is, this is a catch-22 problem: if everyone used the default multiple select, people would know how to operate it (and they’d be able to transfer their knowledge from how the control works elsewhere in their os to the web: for example, if you know how to select multiple files in Finder, Windows Explorer or in a open file dialog, it works exactly the same way in the multiple select control). But, because web developers have decided to invent a 1,001 different multiple selects, the default control is inaccessible.

The real issue I have with the web is everyone has broken user interface consistency across the platform with custom web controls where the default controls would be fine.