To answer the “big question”, “Why Android even allows this” I asume you are taking about the Android versions that are coded to allow this. In this case it is because , well, are coded like this. Why did Google coded their Android version like this? Profit.

Apple, doesn’t code ios like this cuz it is not their big revenue.

I am not sure Google or Apple are the hero in this story. Insinuating Apple does it out of the goodness of their hearts is naive.