I don't know - what about Avid / ProTools and quite a few other specialised AV products that can really only do one thing? They're not mass market products, and it's not exactly a "computer business", but there is a case for specialised hardware.
Even in mainstream IT, there is clear division between the kinds of software you run on a client machine (desktop/laptop/workstation), a Linux server, a Windows Server and other platforms such as IBM Power, SPARC etc. Plus specialised GPGPU platforms, FPGAs, and I'm sure there are a few others.