Fanless implies low power. The problem with low power is that it doesn't market itself well, because it implies a weak CPU. The biggest marketing claim that laptops tend to have is how fast their CPU is, and that's what most people look at when buying. Making it fanless means that you have to get rid of the heat by making the case heat-conductive, which means making it out of metal instead of plastic, which is more expensive. So, most laptop makers have gone down the route of including as fast a CPU as the price of the laptop will allow, which means including a fan and using a cheaper case material.

I bought my Asus UX305C about five years ago now. It's fanless, and the CPU is definitely a little slow, because it's an Intel atom. However, I wasn't buying it for the CPU - I was buying it for the fact that it was fanless, had a decent keyboard, hidpi screen, enough RAM, and sturdy metal case. I don't need a fast CPU, because everything I do is run on a chunky server somewhere else. It feels like an expensive laptop because of the metal case and nice screen.

I was so pleased with it that I recommended an Asus laptop to someone else, but unfortunately that one does have a fan, and the case is made of plastic, and it feels really cheap. The touchpad stops working properly when you hold the laptop case in a particular way, which bends the plastic and stops it being able to detect fingers.