Do you also think businesses shouldn’t need to be “forced” to deal with accessibility? Web devs shouldn’t be forced to deal with accessibility either right?

Web devs aren't forced to deal with accessibility either, unless they choose to work with or for an entity that requires it. No one is coming for your self-hosted blog because its not ADA-compliant.

But if you want every restaurant to be forced into labeling, you will see the small restaurants claim all the allergens are used and they cannot protect against cross contamination.

The FDA prohibits blanket labeling of allergens. They might be able to get away with it but it wouldn’t be legal.

This is a dumb conversation because the landscape of the discussion is one where the costs increase exponentially as the disability being serviced becomes more rare, and there isn't an objectively correct answer.

Maybe, but going by that 5% of the population have severe food allergies and only ~1% use wheelchairs, so if we accept wheelchair ramps etc. as being a worthwhile investment (which I do) then proper labeling and disclosure of allergens seems reasonable as well?

The labeling and disclosure is pretty much solved. The killer and the cost monster is the handling. That's why you see that "Processed in a facility that also processes XYZ" label on some foods.

I had an old coworker with a severe milk protein allergy. So bad that he would get a reaction if he (lip) kissed his wife after she drank milk or had ice cream. So eating out was basically impossible, because his food would pretty much need to be made in a totally separate kitchen to avoid any contamination risk.

So we are right back at my point. Do we force every restaurant to have a secondary allergen free kitchen so my coworker can eat there? Or does my coworker just deal with it and stick to vegan places (like he did)?

If your point is that cost doesn't perfectly match frequency, sure, it was off the cuff, but it doesn't change the underlying nature of "accommodating everyone".