Till iOS 13 I was still using SwiftKey and loved it. You guys might be native English speakers, but for many languages in the rest of the world the default Apple keyboard was/is almost useless. Till iOS 13 my language didn’t even have word prediction, let alone being able to talk in two languages without changing the keyboard (which is very common in my country). SwiftKey had all of that for years, so obviously many people use third party keyboards if Apple is too lazy or just doesn’t prioritise a simple keyboard update for other than the big languages.
But only now I can finally switch. Even though many other people probably still can’t or won’t.