It is artificial and made to push more sales.
It is disingenuous to pretend there are no costs associated with continuing support of old hardware, on both the software and hardware side, not to mention the drag on the ecosystem when older, slower hardware must continue to be supported.
Also bear in mind that the #1 competitor, Microsoft, are traditionally funded from software sales and support - their own-brand hardware business is tiny c.f. Apple, and while obviously they get a tithe from every PC sold with Windows (which is a
huge number of PCs) they also get a shedload of licensing income. MS have a large presence in the corporate market who tend to hang onto old hardware/software
but will pay annual license/support fees, giving MS an income stream from supporting "legacy" systems. Also, Windows has been so dominant that 3rd party hardware makers are pretty much obliged to support Windows themselves to protect their own reputations.
As for Linux, legacy support comes from a mixture of "enlightened self interest" (people who need/use/profit from the legacy tech themselves) or, again, companies that make money from paid support.
So, of the big players, Apple are the ones most dependent on ongoing hardware sales to fund their software development. Where they
do sell software, it's actually fairly cheap (compare Logic or FCP with Ableton or Adobe...).
Will be interesting to see whether or not the M series receives longer OS support than its predecessors. That aging army of M1 MacBook Airs could be passed along to friends and family members, possibly being their first Mac.
It
should be easier to support when the whole system-on-a-chip is made to Apple's designs & specs and they're not so reliant on third parties like Intel, NVIDIA, AMD, Broadcomm etc. supplying updated/fixed drivers. There are also less permutations of hardware (bear in mind that, with Intel Macs, even something like "6th gen i5" was just an umbrella brand for a whole range of different chips. Often, the contemporaneous MacBook Air i5, MacBook Pro i5 "2 port" and MacBook Pro i5 "4 port" had completely different CPUs).
Meanwhile the Mac Pro hasn’t been updated in how long?
Pick one: Apple Silicon or Mac "Big Box'o'slots" Pro.
Apple Silicon has been a success for the laptops, tablets and small-form-factor systems (as has the A-series for iDevices, which shares a lot of tech) which are Apple's bread and butter.
Unfortunately, for a big, sweaty PCIe workstation (who's primary function is to support high-end PCIe GPUs) Apple Silicon is simply not the tool for the job - and the uncomfortable truth is that high-end workstations ceased to be Apple's bread and butter once it became possible to do serious video editing and 3D on cheap, commodity PC hardware - so Apple probably aren't going to invest in making a new, PCIe oriented chip.
Apple Silicon doesn't have the PCIe bandwidth to drive a bunch of high-end discrete, 16-lane GPUs because the
whole point of Apple Silicon is to focus on iGPUs sharing unified memory and lots of on-chip Thunderbolt/USB4 connectivity.
The 2023 Mac Pro is a kludge, relying on the spare SSD interface on a M2 Ultra, for people who really need to plug in a bunch of mid-bandwidth PCIe cards - typically specialist A/V interfaces - for which TB4 couldn't quite cut the mustard. If that's not you, then stop worrying and learn to love the Mac Studio
They've probably sold as many as they're going to & most of those people won't be in a rush to upgrade to M3. If a M5 Max comes out (which could update the PCIe to v5) then
maybe - but I'd be unsurprised if the 2023 isn't just a last gasp while the A/V pro users upgrade to Thunderbolt kit.
Possibly Apple will go off in a different direction and make a "pro" chip focussed on AI creation - but that would be very different from the Mac Pro and - again - probably focus on Apple Silicon's strength by having the CPU, iGPU and Neural Engine sharing (lots of) unified RAM.
