...while you happen to have the Ctrl key pressed down: One function (vertical scrolling) invoked by an ordinary interface device; another function (zooming) invoked by ordinary interface device + modifier input (=Ctrl key, extra finger, etc).

Good for those of us who like handy shortcuts, bad for those of us who are -- or, with increasing age, are ever more becoming -- fat-fingered feeble-fumblers. For those of us who belong to both the aforementioned groups... Hard to say.