[somebehemoth]

While I agree with what you are saying I have a minor nit: "For websites instead, pinch to zoom exists for a design deficency, mostly for web pages not optimized for small sized screen."

I understand what you mean, but in the context of sites specifically disabling zoom it seems to me that pinch to zoom is a design feature and not a deficiency of traditional web pages. Responsive helps, but there are definitely times when I wish the developers would provide only a desktop view so I can use my browser features to optimize my own user experience. (I am not representative of the general public, I know).

[systoll]

Non-zooming sites can (and should) honour your system-wide font-size setting, giving you the ability to use the system's settings to achieve uniformly comfortable reading experiences across websites and apps.

Zooming doesn't do much to give users much control over the reading experience -- iOS does not let users set or change the viewport size, so everyone gets the same columns to zoom into/out of.

If you want text bigger than the single size the designer decided on, you're forced to scroll along each line of text -- which is a terrible experience.

If you wanted it smaller, zooming out won't 'reflow' the layout, so you'll just be losing screen real estate to peripheral content.

[somebehemoth]

I meant to refer to the ability to zoom in on images for the purpose of observing greater detail (which I did not include my comment). I do not disagree with your comment.