[zepto]

Not everyone can use a trackpad.

[aesthesia]

I’m curious: when would someone be able to use a touchscreen to pinch to zoom, but not be able to use a trackpad to make the same gesture? Is this an accessibility issue or just a question of what hardware is present?

[zepto]

An accessibility issue. Plenty of people with RSI for example can use a vertical mouse or other adapted pointing device, but not use a trackpad.

Orientation matters a lot.