They did the licensing thing in the mid-90s. Mac clones were a thing.
To license macOS means to support infinite hardware variations, and to rely on OEMs not to suck. It is an impossible technical problem for a company whose whole ethos revolves around integration of h/w and s/w.
Kind of.
Apple had to approve any clone designs. It wasn't as willy-nilly as the PC market. At the time Apple allowed cloning, Apple itself had a large number of varying models to support.
Apple's big problem was that the clones were faster and cheaper. For example, the Umax C500 was available up to 240 Mhz while the PowerMac 4400 was only available up to 200 Mhz and the Umax machine was $400 less expensive and that was on the low end.
Power Computing's clones were high end and either matched or outperformed their Apple equivalents for less money. The PowerTower 200e was released the same day as the PowerMac 9500/200 and it was $1300 less expensive.
In the really high end, the Daystar Genesis MP smoked everything in Apple's product lineup.
The cloners were bad for Apple but only because Apple couldn't compete with them. Developing both the hardware and the software was too expensive for them to not be able to make all of the profit on every sale.
Plus, we are in a different world these days. Intel hardware, due to Intel's keeping the bus proprietary and getting rid of the chipset makers, is a lot more generic than back in the day. NeXT and a lot of open source projects today have a list of hardware you can use. The list for today is a lot shorter. I think a lot of companies would thrive on making good macOS machines.
I really think Apple should just stop making any PC other than the MacBook and iMac lines. That's where their heart is anyway. License the OS for $250 a pop and sell for the same. If they are that concerned about what happened before, limit the sold macOS to Xeon cpus only. That will get rid of all the portables that might reduce their MacBook sales.
Windows is not inherently bad. But the premise of it working everywhere means some trade-offs are made. Same for Android.
Also, systems would be available to suit power users - Apple currently offers exactly zero in that space. Power users influence many buying decisions beyond their own systems. It would be good if macOS could be seriously used for hard-core science and engineering.
It's a $25B business that's steadily taken significant market share from Windows/Linux over the last decade.
They should give this up, why?
I'm certainly not advocating giving macOS away or selling it cheaply either. It's worth pointing out that every 2,000,000 units of $500 macOS would be $1 billion as well - which could quickly come close to the margin on that $25B.
I don't understand who these people are that are spending a 50% premium on components that are two to three years old. I use a MBP regularly, but only because my work buys them.