If up to 75% of paying customers browsing on mobile use safari would you serve them a broken website? Remember that 100% of browsers in iOS is safari. Everything else is just Safari with a skin. If I could I would block apple users out with a warning about their broken browser but I doubt any business survive for long if they had a habit of leaving money on the table.
Iphone users aren't allowed to install Chrome. They want chrome, but all they get is a shitty chrome skin on Safari. It does trick a lot of people into thinking that they actually have chrome though.
In the US, I assume? Also, note that app stores aren't the only revenue, and precisely because the web does not work as well on ios devices, this number will be slightly biased in apples case.
It appears to be globally, though it depends on what you count exactly (65% of the total revenues, I was off sorry, but 80% of all subscription revenues). The reality is that the hundreds of millions in poorer countries with Android spend peanuts compared to rich countries.
https://www.businessofapps.com/data/app-revenues/
But whatever the exact number, the point stands. In most cases, not supporting iOS is a silly business decision.