Really??
The convenience, portability, ease of use etc of an ipad is a massive appeal to the public, especially those who aren't tech savey or just don't want to bother with the operations that come with a Mac or PC. In particular older people or younger children and like most things, people buy into the name which is always going to be in Apple's favour. Cheap to manufacture with massive margins suggests the iPad is going nowhere. This is a far cry from the desktops which are expensive to manufacturer and support and just don't have the same convenience or appeal anymore. Whilst there is always room for macs and PCs in for certain usages (gamers, photographers, web designers etc) in general they have lost their appeal for general family usage. My wife has hardly used my PC since she's had hers. She can do everything from the comfort of the sofa.
Please re read. High end iPads.
At the moment, to continue selling vast quantities of expensive iPads, Apple are continually having to innovate, which costs them money. The majority of their sales comes from older iPads, or the lower end models like the new 2017 model.
Phones are getting bigger, and laptops smaller (for a given screen size)
Even Apple know that people aren't buying iPads as much, hence the push to make iOS on iPads more like MacOS. They've even introduced the dock now.
People want tablets, but need computers.
At the moment, the high end iPad market is like the Mac Pro market. It's dying - Apple don't sell enough of them to warrant innovation every few years.
The current Mac Pro has the same specs from 2013!!
I still don't think the Macs will go anywhere for the time being. They'll introduce evolutionary upgrades every year or so, and that will be that. Same with low end iPads.
Sales stats say the opposite...yes all make money but Ipad and iPhone make massive amounts more
Sales are lower, but VS the amount of money Apple have to put into selling them. They (Macs) take little resources.
Adverts, new technologies (Apple even have to bring out new CPU designs for the top end iPads) - these are big costs for a rapidly declining market.
Apple aren't stupid, they know what makes them the most money. Hence why iPhones are such incremental updates every year. As much as it sucks, it makes them the most money, so why would they change? People are still going to buy iPhones.