Because most people don't own Macs. The last Windows compatible version of Safari was back in 2012 or so, and as far as I know, it was never available on Linux.
Therefore, for me to test on Safari, I either have to spend thousands to buy a laptop, or pay out of my pocket for some sort of cross-browser testing tool (even if it's free, I am spending extra time) while Chrome/Firefox are used by most of the world and ensuring that I deal with Safari's idiosyncrasies does nothing much for me.
> It's Chrome that has an weirdass non-standard UI (the practice of showing app preferences/dialogs in a webpage needs to burn in the flames of Hades) and other niggles, not to mention being a privacy black hole.
I would argue its more standard since it is the same UI in every OS I wanted to use. I honestly don't think people are that angry about preferences as a webpage.
In terms of privacy, Firefox kicks Safari out of the water, and in terms of performance, it is faster, and actually renders everything (something Safari fails way too often at).
> "most" Mac users wouldn't give a fuck about Chrome.
Eh. Safari not rendering elements of the page, constantly crashing, and other myriad of issues do well enough to push people to Chrome/Firefox. Also, most people quickly start using Firefox when they realize that UBlock Origin doesn't work on Safari and is easily better than anything that comes on Safari.
Honestly, for me as developer, Safari is the new IE6, except possibly worse because bugs for IE6 are very well-documented with good workarounds.