Also, Pascal is a direct descendant of a very, very old language (ALGOL-58 from 1958). In the 1950s, HLL compilation was at the extreme edge of what computers were capable of doing and a key goal of language design was (or should have been - cough COBOL cough) to make it as efficient as possible.

By the time Ken Thompson was designing languages, hardware had improved a lot and he could make compilation efficiency a lower priority.