In general why do sites or apps feel the need to block this, drives me nuts.

It used to be the case that if zooming was enabled, every normal tap would have a 300ms delay on iOS Safari. Iirc they fixed that since (not sure how, can anyone recall?). But basically most mobile web apps built a few years ago would disable zoom so they got snappy interaction.

<meta name="viewport" content="width=device-width, initial-scale=1" />

The "width=device-width" is the cause.

No, this would only set the initial viewport, it does not prevent zooming

Does not block zoom for me on ios 13.3.1 safari.

I stopped using Chrome in iOS 100% b/c it gratuitously honored every whim of any designer/developer to limit my ability to zoom into the screen. Safari has proven to be much less likely to prevent the same. On this x410.dev site I can zoom in on both, but I headed over to flickr to get that good chrome no zoom cortisol hitter.

I don't understand how this isn't an accessibility issue. My eyes aren't what they used to be and it's nearly impossible for me to see content some times. Yet enabling the actual accesibility features in iOS goes way overboard.

Drives me insane.