Those problems are pretty easy to solve. By your logic apple should not allow 3G sim cards in iphone either, but they do. And shitty wifi networks should be banned, but they aren't.
Besides that, Apple can’t control the entire worlds cellular and WiFi coverage. Some parts of countries only have 3G, some buildings only have shity WiFi. However, Apple can control how their iPhone’s storage performs by not allowing you to use crappy SD cards and just having you opt for more internal storage.