[jfultz]

Surrogate pairs were new to Unicode 2.0. Unicode 1.0 didn't anticipate the need for more than 65,536 code points (who would ever need more?); the main perceived threat to that limit having been resolved by Han unification.

[eviks]

Ok, but that doesn't answer the question; it's more of an indication that those design(at)s didn't uncover "the true extent" until years later