The thing is, there aren't really any successful greenfield developments in these types of business spaces. So either these are industries that are exceptionally difficult to break into (which I think is at least partially true), or the type of computing they do actually benefits from being done on a mainframe (which is also true given that there is a lot of record processing for these industries, and not too much serving lots of web requests to users).

Of course, all of these companies also have x86 servers that run the customer facing web apps and stuff. You really wouldn't want to waste your MSUs running web servers, although I'll admit I don't know if these new Linux mainframes are charged by rolling avg MSUs or other MSU metrics. Traditionally, Linux on Z has had more favorable pricing due to the ability to use IFLs and basically just declare that a cores MSU usage doesn't count towards your licensing since it's been locked to only running Linux.