> all too often there are silly things like not letting you tab to the next field

Well, that's a criminal use of client-side validation, but it shouldn't condemn all client-side validation.

> Not to mention it's easier, whether you agree or not with "developers are expensive so performance doesn't matter" in a world where this is often said I'd expect more server side only validation because client side validation is duplicating the work.

That's fair, but as others have noted if you're in a world where a polished user-experience really makes a difference or is a competitive advantage I'd argue that well executed client-side validation can get you to a UX-quality bar that no amount of server-side validation can reach (edit to add: server-side validation is still, of course, absolutely required).

Whether that's truly important for a given business or product can only be argued on a case-by-case basis. I think it's definitely a colorable argument that there's some overuse of client-side validation relative to product goals, but I think there are definitely places where client-side validation is hugely impactful.

Again, all of this assumes that the client-side validation is implemented at a high quality bar. Of course bad client-side validation is not useful.