Even when you CAN do this, it’s usually because the employees are either kind enough or inattentive enough to let you do this. And if you are clearly unhoused or poor, your chances of being able to do this are much, much lower than if you can fit in in a middle class white area. (Restaurants with predominantly poor clientele or many homeless people nearby tend to be much stricter about this.)
I think most people objecting to it are primarily objecting on moral grounds, not legal ones.