Backward compatibility ...
One thing this otherwise excellent article doesn't really address, and is the *real* reason we are where we are.
PC/MS-DOS were inherently flawed, as they were single-user in execution, they had no concept of root and user access. Whoever switched on the machine was king of the hill. And this paradigm carried on throughout the 1980s and 90s - right the way up to Windows 95.
We *could* have had a true multi-user multi-tasking PC/OS combination in 1987. But the second business realised they would have to pay for new software to run on OS/2, the die was cast.
Excellent reading and discussion material for a Friday. It's like being back at Uni ;)