Why Are There So Many Programming Languages?

Long-time Slashdot reader theodp writes:
Recalling a past Computer History Museum look at the evolution of programming languages, Doug Meil ponders the age-old question of Why Are There So Many Programming Languages? in a new Communications of the ACM blog post.
"It's worth noting and admiring the audacity of PL/I (1964)," Meil writes, "which was aiming to be that 'one good programming language.' The name says it all: Programming Language 1. There should be no need for 2, 3, or 4. [Meil expands