The problem with touch screen is, if you are an unfortunate person wwho has hands that shake a bit for whatever reason, a mouse is easy to use, jut touching a screen is iffier----I can write, draw with my hands, but not control simple "touches" ---!
The problem with a touch screen is, that if you are unfortunate like me to have hands that shake a bit, simple touches on a screen can be iffy. I can write cursive with my right hand, I can draw rather well, but simple 'touches' are more difficult. A mouse is much easier to control than poking my finger forward. Why can't Apple take special physical needs into account like mine - which has no diagnosis - and all those with parkinsons, cerebral palsy, and any other movement problem and allow them to use a mouse with an ipad and enjoy it as well?