>Why would Apple care if Mac users used a [non-]Safari browser?

Apple doesn't care individually what users use. However, Apple (and everyone else for that matter) does have reason to be concerned about Google's Chrome completely dominating the web in the way IE once did. iOS is certainly their biggest bulwark, but that doesn't mean they'd be delighted if Mac users felt required to use Chrome. Further, they also have made being able to avoid the anti-privacy ad-driven ecosystem to some extent an important differentiating factor. Even with Firefox existing, having a purely Mac focused and maximally optimized browser (FF is only barely catching up this/next version on basic power efficiency for example) that has strong privacy protections with no conflicts of interest is a sales point.

That doesn't mean it's a total core focus of course, but neither is there no pressure at all.

If every single Mac user used Chrome, it wouldn’t matter. The market cares about Safari compatibility because of iOS.

Just like most printer manufacturers don’t focus on AirPrint compatibility because of the Mac. That’s just a byproduct of iOS compatibility - which they do care about.

It's quite important that developers actually test their desktop layout and functionality (hover states, etc which don't work on a touch screen) with Safari's engine.

If a site doesn’t work with desktop Safari well, you can tell them to just use Chrome.

No, that would be precisely the problem!

We don't want websites to be written for compatibility with a single browser engine. That means developers are writing to Chrome's quirks, not to actual web standards. Over the long term, that gives Google complete control over how the web is run.

There are currently between 3 and 2.5 browser engines that matter, depending on how you count webkit vs blink. I'd really rather that not fall down to only 2 on desktop.

I’m not saying what we want I’m saying that whether we want it or not, it doesn’t matter whether Safari’s desktop market share drops from the current 3.6% (https://netmarketshare.com/browser-market-share.aspx?options...) to 1.8%, it won’t change the calculus on whether web designers care about desktop safari when they can just tell people who are complaining - use Chrome.

It makes a big difference for me, at my job. 3.6% is enough users that I can justify spending (some) time to test and fix bugs. As that number approaches 1%, however, it gets much harder.

and the total usage of safari across all device types allows for a certain percentage of users in the wild which acts as the size of the lever apple wields for changes they want (or don't) in the specs.

Last time they posted numbers, they were selling around 200 million iPhones a year, 45 million iPads and maybe 20 million Macs. The Mac market share is insignificant even to Apple in the grand scheme of things.

Any web standard is useless without Apple being on board. Developers either won’t implement it or create an app for iOS to use a feature they need.

Even with your numbers, 1/10th the sales for a more expensive product isn't insignificant. It's especially important for their brand value as a tech company.