I am not the right market for flagship phones because I don't have thousands of dollars to put towards disposable income, but I would expect a premium phone to come with a premium warranty and repair service... Do they typically not?

No they don't. Even waterproof phones damage due to simple water spill get denied warranty (even from Apple).

https://www.apple.com/applecare/

AppleCare specifically covers water damage of any kind, and is what I would assume OP would be referring to as a "premium warranty and repair service".

That isn't my read.

ApplecCare is as much a warranty as their Apple's phone are guaranteed waterproof.

It's marketing.

The 3 year warranty add-ons is an insurance. One can get an insurance for any device.