The problem with "service" dogs is that you can buy a vest on Amazon for $25[0] without that dog having been trained to do anything in particular. Many people (in San Francisco especially; I'm surprised you haven't seen this) just put these on their dog and claim that they can bring the dog into restaurants (where non-service animals are specifically banned by health code).
The whole "emotional support animal" thing has been abused like crazy by people who just feel entitled to bring their pet anywhere they want, regardless of the law, or even just the policy of a particular establishment. Generally it's fairly legally perilous for a business owner to attempt to ascertain if the animal is really a service animal that's been properly trained to do tasks for their human, so they often feel stuck and unable to turn them away.
I like (most) dogs just fine, but I don't want to be seated indoors in a restaurant one table over from one, even if they're well-behaved. I'm fairly allergic to some breeds, and I don't want to spend my meal with itchy eyes and a stuffy nose. And I certainly don't want random pets walking around grocery stores, sniffing the produce and shedding hair on everything. Actual service animals are trained to handle those situations properly and not be a nuisance, but your random pet or "emotional support animal" is not.
[0] https://smile.amazon.com/Service-Vest-Hook-Straps-Handle/dp/... for example