As a rule human processes and technologies evolve in response to perceived problems and opportunities, but then freeze into place until some sufficiently powerful external force is applied to dislodge them.
Prior to WWI and the Spanish flu, for example, a lot of Europe's aristocracy (and military leaders) reacted to the evolution of the horseless carriage by having theirs drawn by horses - and COBOL, when adopted for digital data processing in 1958, both implemented the the 1930s machine instruction set and inherited its card processing model in which a prepended card set (now expressed as JCL) effectively created a virtual machine environment for each job.
By the late 1950s, however, it was becoming clear that CPU costs and performance were significantly outstripping memory development and therefore that a way had to be found to more effectively share the CPU between processes.
From that three solutions evolved:
Absent compelling force people continue doing what they know so zOS still implements 1930s procedures, data processing people moving into Wintel management positions have brought virtualization and related ideas with them, and IBM recent defense of a press release claiming a $26 million z10 the equal of 1,500 dual core Sun Opterons costing a cumulative $1.8 million provided that 1,350 of them are idle hasn't moved the industry to gales of laughter.
But it should have - and sooner or later it will, because IBM's own numbers show beyond all reasonable doubt that the first two solutions: partitioning and virtualization, make about as much sense today as hauling cars around with horses.