The mom and pop store making $200k/yr revenue selling physical goods gives regulars a deal because if their $100/mo spend goes elsewhere it is a demonstrably negative business impact, and there are 2 or 3 other mom and pop stores close by. The owner's kids also probably go to school with the regular's kids or there's some similar relationship. Plus, even if they wanted to maximize profit - they probably don't based on the previous point - they simply don't have enough data points to figure out how exactly to do it.

The multinational corporation has billions or tens of billions in revenue, tens or hundreds of thousands of locations, and so many data points they can test any price discrimination scheme they want and get data almost instantly. But this by itself isn't a problem (IMO, certainly some here would disagree). The root of the problem IMO is that there's no relationship. The manager of the location has no power, the district manager is in a city an hour away, the people making these pricing decisions live in another state or country, and they are judged on making the graph go up and to the right. Their bonuses depend on it, their livelihood depends on it.

In the mom and pop scenario, the customer interacts with someone whose livelihood depends on them being happy and has the power to make sure they are. With the multinational, they interact with someone who doesn't give a shit if they're happy or not, and has no power whatsoever, and the lowest person with power doesn't have any idea who they are and is actively incentivized to screw them.