Alan Kay, one of the lead developers of Smalltalk, said it was also valued for being good for bootstrapping ideas for building
systems. He went into that topic starting at 58:50 in this talk:
Alan Kay at OOPSLA 1997 - The computer revolution hasn’t happened yet
https://www.youtube.com/watch?v=oKg1hTOQXoY&t=3530s
“To me the most distressing thing that happened to Smalltalk when it came out of Xerox PARC was for many respects and purposes it quit changing. Now I can tell you at Xerox PARC there were four major versions, completely different versions, of the language over about a ten year period. And many dozens and dozens of significant releases within those different versions. And I think one of the things we liked most about Smalltalk was not what it could do but the fact that it was such a good vehicle for bootstrapping the next set of ideas we had about how to do systems building. And that for all intents and purposes when Smalltalk went commercial ceased. Even though there was a book, the famous blue book, that Adele and Dave wrote that had the actual code in it for making Smalltalk interpreters and starting this process oneself, almost nobody took advantage of this. Almost no university took advantage of it, almost no commercial institution took advantage of it. And what they missed was, to me, the deepest thing I would like to communicate to you today, and that is we don’t know how to design systems yet. So let’s not make what we don’t know into a religion for God’s sake. What we need to do is to constantly think and think and think about what’s important. And we have to have our systems let us get to the next levels of abstraction as we come to them. And the thing that I’m most proud of about Smalltalk, pretty much the only thing from my standpoint that I’m proud of, is that it has been so good at getting rid of previous versions of itself until it came out into this world. Now one of the reasons we got involved in doing Smalltalk talk again, for me it was after 16 years of not working on programming languages, a couple of years ago we started this project we called Squeak, which is simply, not an attempt to give the world a free Smalltalk, but an attempt to give the world a bootstrapping mechanism for something much better than Smalltalk. And when you fool around with Squeak please please think of it from that stand...think of how you can obsolete the damn thing by using its own mechanisms for getting the next version of itself.”