Walmart is the App Store, Apple is the town, and Epic is the fertilizer company wanting to open a farming supplies store of their own because all the farmers already know them from farming fairs and word of mouth so they don't really need the exposure from being on display in Walmart.

I don’t think Apple is the town. A town is something that a user (resident) should feel comfortable staying with their whole life. However, it is perfectly reasonable for a person to pickup a new phone from a different vendor on their next upgrade cycle. Therefore Apple can’t be the town. Apple is Walmart and Samsung is Target and the 100s of other Android devices are other stores.

The town is a good analogy because switching towns – like switching phones – is a significant expense relative in either case, while switching stores is free.

Interesting. So is the goal of regulation to ensure it's easy for people to switch "towns"? What if Apple, Samsung and Google needed to make it simple and easy to switch between their respective platforms, to a best effort? For example, if they both had similar cloud photo storage they would automatically exchange those. In other words, if we can make switching mobile ecosystems as easy as switching stores then we shouldn't take issue with Apple or Samsung or any other mobile platform. Market forces alone can influence how each company runs their business.

Sure, if you can switch from a Galaxy S10 to an iPhone 11 for free, then your argument might apply.

Apple would just have to take other phones as payment for their phones, and the same in reverse.

The issue isn't one of technology, it's that you're pretty much locked in after spending a lot on a phone.

I don't know about that. How is this different from Costco selling a membership for a year? You've just paid up front for access to Costco for a year and now you are "pretty much locked in". Why doesn't a cookie company sue Costco for better placement the ability to pay for those cookies with cash directly to the cookie company? Those poor customers are locked into Costco and have to live with Costco's choices on which products to stock, where they go in the store, and pay for them through Costco checkouts.