>>1
For the same reason Forth is dead: the language gives too much freedom.
Forth and Lisp are similiar but also very different, both give the programmer the ability to extend every part of the language, creating DSLs, and have a consistent non-syntax. The only difference, is that the Forth programmer works near the hardware, at low level, where the Lisp programmer works on top of an abstraction layer, creating more abstractions.
They both are the ultimate languages, they gives you everything you need.
That's the problem with them, you need to master the language, understand it, start thinking in it, become one with it to use it properly.
If we only had these two essential languages, programming would really be something ``for smart people only''. (and learning the art of it would also really make you smarter)
"SQL, Lisp, and Haskell are the only programming languages that I've seen where one spends more time thinking than typing." -- Philip Greenspun
The Fortran/Algol branch of languages has become more widespread because they are braindead.
Pick a random language from that branch, you'll see that they have hardcoded, ``nice-looking'' statements for the most common operations, such as loops, ifs, etc, all of them with a different syntax. This makes them easier to learn for non-programmers, at the cost of the programmer's freedom and power.
Then, C and UNIX came, UNIX was a really simple system, everything was a file and didn't have a versioning filesystem. It had flaws, many flaws, you can read some in the UNIX Haters Handbook, but most of the problems it addresses don't apply anymore.
So, C was inferior to Lisp and Forth, UNIX was inferior to Lisp Machines, why in the world they replaced them?
They are simple, everyone can use them without having to think and learn how to use them.
C is a static language, you've got if, while, for, goto and return, you must use these and nothing else, you can't add anything to it.
In UNIX, everything is a file. The concept of a file, without attaching versioning informations and such to it, is really simple, everyone can understand it. Could you explain your grandmother how a file in a complex versioning filesystem works? I can't. Could you explain her, instead, what would it be in a simple filesystem? ``You write your stuff in this file, then you archive it, when you need to modify it you take it again and do your modifications, then rearchive.''
The time passed, and we developed a Stockholm syndrome torwards UNIX and Fortran-based languages.
The Lisp/Forth-aware people can't do anything but suffer in silence.
It's sad, but the men it's just limiting its evolution.