One reason for disabling pinch zoom on mobile is that it allows click events (taps) to be registered immediately. When zoom is enabled, there is a 300ms delay t

One reason for disabling pinch zoom on mobile is that it allows click events (taps) to be registered immediately. When zoom is enabled, there is a 300ms delay to see if it was a double tap: if a second tap happens during that 300ms, then the browser zooms the page instead of firing a click event. (Unfortunately, there is no way to disable "double-tap to zoom" while keeping "pinch to zoom" enabled. It's all or nothing.) Some people don't notice it, but I do and I find that sites do feel more responsive when zoom is disabled.