You're right that we don't need a universal definition of hamburger. That's because the government stays out of it, so private individuals can use things like Google Maps reviews to police a common sense definition of hamburger along with quality and other nuance.

If governments were forcing everyone to buy anything advertised as a hamburger no questions asked, then the definition of hamburger would matter a lot.

The devices on my desk are 99.9% the product of the private sector and owe nearly nothing to academia.

If people can't define it, then that seems to me like a valid criticism of the scientific method. You can't have institutions that claim to be doing science if they don't use the same definition of science as other people do.