Nowadays, people want to have a phone and a laptop. Tablets are dumbed-down computing devices, for kids, the elderly, or as toys for the rich.
I don't have some deep moral objection to software walled gardens (if that fits your use requirements, more power to you!), but if that model ever wins out, it will be a sad day for innovation. Software's one of the most powerful tools in recent history for disruption, and having a centralized entity wield control over that creates a dangerous bottleneck for this relatively new, extremely powerful medium for human expression. Good to see that, on at least some level, the market agrees with me.
PC sales were 60 million, taking Apple's share of 4.2 million, it's 56 million, give or take.
Last year, Apple in this period sold 51 million iPhones, 10 million iPads. And it was a "bad" year.
You might say "but I need my desktop, my IDE, my Photoshop, my etc."
Yeah, but you are one programmer or photographer or video editor, most people don't create anything, or just do some very light editing (like removing skin imperfections from photos), and thus, a media consumption device is most right.
We are in the Post-PC world, live with it.
Sources
Apple: investor.apple.com IDC: IDC Worldwide Quarterly Personal Computing Device Tracker, April 11, 2017
Remember when everybody said the Microsoft Surface was a failure because nobody wanted a 2-in-1?
I don't disagree that tablets aren't quite a big thing, but I think we'll see another device which fits more use cases.
The classical laptop has become a product for creation professionals.