It shouldn't be so hard to understand the problem. Let me give you an example. Apple develops a product with components that are doing the same thing as standard components that are ready available at the market. But instead of using those readily available components they make some twist on it just to ruin compatibility. Then they forbid the company that made that component to sell it to anyone but Apple. That basically gives Apple a monopoly on repairing the device. You talk about sourcing parts, but in this case no one can source parts except Apple unless they salvage parts from other devices which is not always viable.