I don't know, but I have my hypothesis as well as for why this and other user-empowering approaches were abandoned: the rise of PCs. In the late 80s and early 90s, the first PCs appeared and were seen as the obvious road to computing for everyone. But they were not powerful enough to run environments like Smalltalk. It's Basic we got instead. In parallel, professional high-end computing grew as well and that's where the money was. Academia followed the money.