There's a wild difference in features and ecosystem when using an iPhone, as well as quite some friction in changing, to the point that it's way more than simple brand recognition. iPhones tend to be more expensive, yet they are bought by a wide range of consumers who value them and the Apple ecosystem, the customer support etc. If brand recognition were the main reason for consumers to choose Apple devices, they'd have all switched to Android once they realized they can just pay half.

This friction to switch is just not there for chatbots offering substantially equivalent features. That's why ChatGPT is still mostly free: most users would leave the moment they impose stricter limits. If you know nothing about smartphones but they cost a significant amount of your income, well you try to know more before you buy anything. There's no reason to do that for chatbots yet given that they're free to use, just try it out and stick to the first one you tried until they make it bad enough for you to want to switch.