There is just a lack of good ones, though.
Personally, I don't like the heavy Java and C# VMs at all.
Browser javascript VMs seem to be much more lightweight, which is good for interactive clients, and lately with NodeJS they gain a lot of momentum server-side too.
LLVM might be closest to an universal open source JIT platform. It is used as the backend of many of the language-specific VMs.
There is just a lack of good ones, though.