Coupled languages and programming tools had OK adoption back in the day: Turbo Pascal, Visual Basic, HyperCard. But times have changed, perhaps in no small part thanks to the open source movement.

I used LabVIEW heavily for a few years in the mid 90s. What killed it for me was the sheer physical labor of programming in a graphical environment. All of that detailed mouse work gave me severe eyestrain headaches and wrist fatigue. When I'm typing text, I'm barely looking at the screen. Granted, this may be a personal physical limitation, so I can't offer it as a general argument against graphical programming.

Another issue is that decoupling the tools and the language lets you experiment with new languages and features with a bare minimum of effort. I've even tried out my own toy languages. But building a graphical editor, even a general purpose one that could serve multiple graphical languages, seems like a boatload of work.