There are also validations that can improve UX but aren't meaningful on the server. Like a "password strength meter", or "caps lock is on".
Religiously deploying the same validations to client and server can be done, but it misses the point that the former is untrusted and just for UX. And will involve a lot of extra engineering and unnecessary coupling.
That said, I could definitely see additional checks being done server side. One example would be actually checking the address database to see if service is available in the entered address. On the other hand, there really isn't any waste here either. I.e. just because you write the validation in server side JS doesn't mean you MUST therefore deploy and use it in the client side JS as well, it just means you never need to worry about writing the same check twice.
Also, in my opinion things like you suggest you shouldn't do. A password strength metre is only going to give attackers hints at the passwords you have in your system. And I have not see a caps lock on warning in forever. The only password validation we do is the length which is pretty easy to validate on client and server.
No, it's not. A password strength meter just shows you the randomness of an input password, it doesn't have anything to do with passwords already in the system.
You still need the client side validation for UX. The regular users needs to know if they messed up someting in the form. Also it's a much better UX if it's done on the client side, without the need to send an async request for validations.
<input type="email" required placeholder="Please enter your email address">
Server side validations predominately enforce business constraints.
If you mix the concerns, either your UX suffers (latency) or the data suffers (consistency, correctness).