I'm fond of telling people that it's best to get an adult cat, because then you can have some idea of what the cat's personality is like. Do you want a cat who will greet your visitors? A cat who prefers to sit next to you rather than on you? A cat that will remain overtly playful? A stoic cat? Then adopt an adult cat whose personality is already pretty clear.
I also like to say "kittenhood lasts only short while." Then you are stuck with what you get.
However, I can't blame people for wanting to enjoy that "short while." There is nothing as cute and as fun to have around as a kitten. They remind us of what it's like to live in the moment, when everything is new, and it's OK (and even preferable) to be slightly dumb, and surprised by everything we encounter.
I know I'm really enjoying these four I have now. I need to get them FeLV/FIV tested and out of here. Their ear mites now seem to be under control, and they are as friendly as can be. I wish I could say the same of their mother, who still hides in the closet.
There is a reason there are so many kitten videos on YouTube. People just want to take a moment and laugh.
Although there's no guarantee that your kitten will grow up to be Maru.