It’s nothing to do with not knowing better, and much to do with the fact that 20 years ago computers were far more limited. Even today, in a script that generates submenus in my window manager’s root menu and is run every time I hover over the submenu item (and therefore needs to launch, run, and terminate instantly), I had to use Getopt::Std over Getopt::Long because the latter just plain doesn’t load fast enough. Similar concerns exist when writing CGI scripts, which is thankfully a genre in decline. Another related issue might be memory use – big modules eat more RAM just for being loaded.
Put in context as an anachronism, Larry’s justification seems a lot less irresponsible.
Makeshifts last the longest.