Uniformity is an entirely different issue. All browsers can zoom in, regardless of the CSS, but how they implement it is different.
Safari on mobile devices uses a visual zoom which is like scaling up an image, while desktop browsers usually scale up CSS units and reflow the layout with the bigger dimensions.
or users can use a magnifying glass, if they own one
it is not true that all browsers can zoom in. there are some cases, e.g. mobile platform with stock browser, where CSS dictates no zoom and the browser honours this and therefore cannot zoom
that might be due to browser implementation but ultimately CSS dictates it
I have no interest in mobile Safari but its non-vector based zoom sounds useless, and desktop zooming is unreliable
