[jfb]

SICP isn't a book about Scheme. It's a book about writing computer programs. Scheme was used because it imposes the minimum additional cognitive load. Worrying about all the warts in, e.g. Common Lisp (to say nothing about Javascript or Scala, say) would detract from the pedagogical mission of the book.

[lispm]

SICP did not use Scheme. SICP used a tiny subset of an early Scheme.

You can use a subset of Common Lisp and the programs in SICP would mostly look the same when written in that CL subset.

I have a surprise for you: Scheme has warts, too.