I don't think it is major corporate backing -- for example, neither Perl nor PHP had one, and they still are (and always were) vastly more popular than Forth.

I don't think it is major corporate backing -- for example, neither Perl nor PHP had one, and they still are (and always were) vastly more popular than Forth. It seems to me that Forth only works for certain people, and those people are quite rare. For the majority of programmers, almost every other language will make them much more productive.