[starseeker]

It lacks a graphical application development framework that's portable and usable. Java eventually solved this problem (more or less) but neither Garnet nor CLIM ever reached a level where most Gtk/Qt/* programmers would seriously consider using them. Web front ends are find for certain things, but for a lot of the application domains where you might consider Lisp you want a proper desktop GUI application. (This would have been especially true in the early years.) The expressiveness and power of Lisp look a lot less attractive when you run headlong into the practical problems of combining that power with a modern GUI.

There are still a few problem domains (like Computer Algebra) where Lisp provides enough benefits to be worth bridging the gap between its world and modern operating system environments, but by and large the inability to be a complete solution I think serves as a disincentive to use Lisp.

[_ph_]

For portable and easy to use there is LTk, and of course there are bindings to Gtk and Qt. I think though, if the Lisp community were a bit larger, these bindings would see more development and more refinement.