"Some context: Common Lisp did not exist (the effort was just getting underway). MIT Scheme did not exist. Scheme was a couple of AI Lab tech reports and a master's thesis. We're talking the tiniest seed crystal imaginable, here. There was immense experience in the lisp community on optimising compiled implementations of dynamically-scoped languages -- this, to such an extent, that it was a widely held opinion at the time that "lexical scope is interesting, theoretically, but it's inefficient to implement; dynamic scope is the fast choice." I'm not kidding. To name two examples, I heard this, on different occasions, from Richard Stallman (designer & implementor of emacs lisp) and Richard Fateman (prof. at Berkeley, and the principal force behind franz lisp, undoubtedly the most important lisp implementation built in the early Vax era -- important because it was delivered and it worked). I asked RMS when he was implementing emacs lisp why it was dynamically scoped and his exact reply was that lexical scope was too inefficient. So my point here is that even to people who were experts in the area of lisp implementation, in 1982 (and for years afterward, actually), Scheme was a radical, not-at-all-accepted notion. And outside the Lisp/AI community... well, languages with GC were definitely not acceptable. (Contrast with the perl & Java era in which we live. It is no exaggeration, thanks to perl, to say in 2001 that billions of dollars of services have been rolled out to the world on top of GC'd languages.)"
http://www.paulgraham.com/thist.html
(emphasis not my own)
That whole page is a good read, particularly if you are a fan of Shivers' writing style.