Because it doesn't move. When you press down on an Apple touchpad, it doesn't displace at all, it vibrates. This gives you an identical touch response across the entire trackpad, plus nifty things like Force Touch and customizable response intensity.
Nobody else has done it, and it makes every other touchpad feel awful.
Apple can have the best one, sure, I believe it. But they still are bad pointing devices as a type of pointing device. People have gotten used to them, because what else can you really fit into a laptop?
I never found a non-Mac with a trackpad I could use _at all_. I always need a mouse to use my windows laptop...
Trackpads are better than touchscreen interfaces though.
I didn't use a mouse since at least 2006. Before that I was mandated to use one by the company I was working for but I probably didn't. Why should I lose time to move my hand to grab the mouse when it's already close to the touchpad?
I connected a mouse a few times to play some casual game but I'm not playing games anymore on my laptop.
There's actually a few benefits, like touchpad gestures for app and workspace switching being much faster than the equivalent keyboard shortcuts.
According to John Romero, keyboard + mouse was intended:
The Apple one is so good though, it convinced me to buy their dedicated desktop trackpad for when my laptop is docked and I work on my large monitor at the desk. It got to the point where I prefer their trackpad for literally everything I do on my desktop, with games being the only exception. Though I am still fine and good with using a mouse. Trackpads on windows laptops though, it feels insufferable in comparison.
The nipple! I have no idea what IBM actually called it, but that's what it was. I would take it 10 times out of 10 over a touchpad (which I appreciate but cannot use properly)
Apple trackpads are a mouse replacement. There are literally people who have a Magic Trackpad instead of a mouse for desktop use.
That's how good the Apple stuff is.
I have a very nice Logitech mouse and keyboard setup, but still prefer to use the Macbook touchpad while connected to an external display. They're just perfect in every sense.