Why isn't Smalltalk taught?

Introductory CS courses seldom use Smalltalk as the teaching language, preferring instead Scheme, Python, or Java, even though Smalltalk seems (to me at least) to have strong advantages over these languages. Why isn’t Smalltalk taught?

At least one reason might be that there’s no self-contained syntax: you can’t write down whole programs. In situations like exams and quizzes, where students are asked to longhand program text solutions to problems, Smalltalk doesn’t fit well, requiring a browser as it does.

Source code in files means that your programs aren’t atomised as they are when viewed in a browser. I wonder if GNU Smalltalk’s syntax for file-based Smalltalk programs would make sense in a teaching context?