I work at a shop where a few people are JMP users. I think it's a problem when a proprietary app is only available to a handful of users at a site -- they tend to get a lot of work dumped on them, and nobody can use their stuff without going back to them. It's a different experience when a site has a site license.
This isn't specific to JMP of course. A good thing about Excel is that businesses are OK with just paying for "everybody" to have it.
Also, people use Excel for more than analysis. It's also a crude database and platform for creating small "apps" that do things, that are easy to share with others.
Trivia: JMP stands for "John's Macintosh Project".
Also, the entire semiconductor industry depends on JMP just like the entire pharmaceutical industry depends on Minitab.