A food establishment forced to serve you might serve you food that's gone bad, a mechanic might not fully tighten the nuts on your brake pads, or any other variety of horrible things that people could do to harm you while leaving room for plausible deniability.
At least if they can legally deny service to you, you know that the ones serving you aren't a risk to your wellbeing. And to that end, I think it's a bit unfair to suggest that less money means there would be no businesses to serve that group of people. If every restaurant is discriminating, the singular restuarant that serves the less wealthy group would have plenty of business, simply due to the lack of competition.
The "pro-regulation" argument is valid with regard to a less commoditized market though, which is interesting. For example, I wouldn't want the only company that makes a life-saving drug to be able to legally discrimate who they sell it to.
It's a challenging problem and I certainly see both sides. My gut goes to regulations affecting large businesses but not smaller ones. It feels like there are probably some difficult edge-cases within there though.
Assuming that refusal-of-service is a sort of relief valve is wildly optimistic.
Overt but relatively passive forms of racism effectively give pervasive comfort and encouragement to those who would engage in more active acts. Indirectly, this is also why "dog whistle" speech is so dangerous.
Per your example, in an environment where simply refusing service to you was common and widespread, you might find that someone who does agree to serve you is doing so just for the opportunity to spit in your food (at best).
Depends on how spread out the population is - black folk, maybe (but I don't have a simulation on me to work it out for sure and in what situations that theory might collapse), the subset of trans folk who're still working out how to blend in and not be seen as such in a rural area, not so much.
There's entire countries where some products are just not available commercially due to the lower income meaning nobody wants to put in the effort to work out how to provide them cost-effectively.