Because they usually are in a tech bubble where Apple is the best there is on everything and they never really tried any alternatives.

So, they think it's good and it's a delusion because it would not be objectively considered good if it was compared side by side with the competition.

I know that for sure because I have spent a lot of time with people like that and I used to be a bit like that. It's much easier to see the world in black and white for most, just like religions are with good/bad and people who really like Apple stuff are very often like that.