does the iphone xs needs a protective case?

I would say that is entirely up to you.

But it would be best to actually put a case on a iPhone that costs $999+ and has a front and glass and back and stainless steel band. While these may be very durable and hard to damage, it doesn't mean it's impossible.

One fall onto the sidewalk and you've scuffed up and cracked one or both sides.

I would recommended if you like it as that you look into buying a Peel iPhone XS case clear. They are so thin it's like it isn't even there and it will protect the phone BUT you must have screen protector as you would be risking cracking the front of the phone, that or look into a thin or clear case by your favorite manufacture.

I agree with ChrisJ4203.

Does it need (require) a case? Certainly not.

I personally chose to purchase Apple's iPhone XS Leather Case for mine. It's minimal, so the iPhone's look is still very much visible. Yet it adds a little something to the appearance in my opinion, and it's a bit protective. But again the decision is entirely yours.

The decision to use a case or not is completely up to you.