> First of all, the OS does not style widgets, the browser does. This goes beyond scrollbars. There are hundreds (thousands?) of libraries or entire frameworks

> First of all, the OS does not style widgets, the browser does. This goes beyond scrollbars. There are hundreds (thousands?) of libraries or entire frameworks to build consistent dropdowns. Even more to create date-pickers and to replace alert dialogs, add modals, and whatnot. This shows that the browsers don't do a good job offering nice and neat UX on them. Same for scrollbars. Browsers offer native dropdowns (that more-or-less match your OS - depending on browser and OS), datepickers (that at least match your locale) and even native alert dialogs. And many are ugly as hell, have a terrible UX or integrate very poorly. IMO fair points. And often even reasons to replace the native widgets with tons of JS, CSS and dom manipulation. Edit: though I don't think this is the case for scrollbars, I think browsers do a good enough job there. The one reason that I very much disagree with, it cross-browser or cross-platform consistency. No-one cares that widgets on your website or -app are the same on chrome/windows, icebeaver/weirdlinux and safari/OSX. Because no-one other than the webdeveloper and -designer will ever use them on all those platforms and expect everything to look the same on all these platforms.