It's not that complicated. When Apple built their store, they built their model around charging a commission for the sale of digital goods. It would have been unworkable, not financially feasible and insane to think that they anyone would be able to build a model where they charged a commission for every good or service that anyone used an app for. Steve Jobs wasn't insane.
You are free to build such an business and market it to companies. Good luck.
You are also free to argue to companies around the world that they can't sell their own products in their own stores because they have an advantage. Legally, at least in America, we don't prevent such common sense activity by businesses, and I'm sure Amazon, Microsoft, Walmart, Starbucks, Target, Google, etc., would find your suggestion that they not use their platforms to benefit their own products and services an interesting idea.