What's wrong with diversity? I like having the option of a closed wall "curated" market, and an open install anything market. I can do my banking on my iPhone

What's wrong with diversity? I like having the option of a closed wall "curated" market, and an open install anything market. I can do my banking on my iPhone and have the password saved on it, while having an Android running F-droid running whatever I want that will never touch my banking info. What's wrong with having MORE choice. iPhone are no where near market monopoly.