I'll never understand you market share people. Why should Apple care about having the most marketshare when they take the vast majority of the industry profits at the lesser marketshare?
Because there's more to it than just how much Apple makes on the sale of an iPhone. Apple also generally makes the most profit-per-
computer (unit) sold but how much software is available for Windows that is not available for Macs (still... in 2018).
Conceptually, Android could swallow up all but a single (phone) unit. Apple could make that 1 unit and price it at $150B for a $149.99B profit). And then we could all gush: "...but who makes the most profitable smart phone(s)?" to which Apple would surely win. But then you have app developers thinking about developing apps to try to make a living... for that one spectacularly profitable iPhone sold or for the other 99.9% of the market in that scenario?
Somewhere out there in the world there is probably still a Palm smart phone for sale. Maybe a Nokia smart phone leaning on symbian too? Those dead/near dead smart phone OS's might even own .000001% of all smart phone market share even today. Now, put yourself in developer's shoes: do you want to go to the trouble of writing your app for those phones?
Yes, of course, the bulk of profits for developers is apparently still based in the iPhone ecosystem too. But as share shrinks, the attraction to code for broader distribution must rise... much as a developer wanting to make money should code a Windows version before (or at least with) a macOS version, rather than coding for macOS first... or exclusively. Sure, Apple likely makes more profit per computer sold too, but the developer needs to sell a LOT of copies of their apps so that they can make their money too.
Even if we can make some argument about dev profitability, how about accessory makers too? Make your accessory for a shrinking market share or make it for a growing share? Are the accessory makers still doing the engineering to make accessories for Windows phones? (the old) Blackberry? Palm? Etc. Again, profitably may be healthy now but growing market share always begs for first consideration.
And so on. Granted Apple's relative tiny share is tens of millions of units, so the marketplace is not dead/doomed/etc. but anyone able to step back and look at a situation objectively should have at least some concern in shrinking market share... NOT because that spells doom for Apple Inc. or AAPL but how it can impact secondary sales such as apps & accessories that makes Apple products so useful.
To this day, I have to keep a Windows partition on my Macs because I need a fully compatible version of Quickbooks, and clients inevitably have Windows software that do not have macOS versions (or need complete MS Office and similar compatibility instead of just partial compatibility). Such clients don't give a hoot about how much profit Apple made on the sale of my computers to me... only if my tools can do the job they need done.