Sparc machines were not as good at number crunching as Power so Sun wasn't as well-represented in the list as IBM, and Solaris wasn't as heavily used as AIX.
I’m specifically referring to running HPC on SmartOS, which runs only on intel and AMD, with full support for intel only. My question is why isn’t it used for HPC now since it provides CPU bursting, not why it wasn’t used in the past. Fair disclosure: I grew up on SGI and HPC, I know what was before.