That's what I meant to say with the security reasons comment. If that's not what I said your comment is an adequate clarification.
Basically you can't trust the guests and the guests can't trust the host as well. Contracted hosting is an interesting situation because neither group can realistically trust the other with their data because they don't screen each other's employees. Maybe there are hosting companies that offer to assign management screened by the contractee but it would seem easier to just put your own server in their rack and manage the whole thing yourself, otherwise you have to deal with a situation where no one can trust each other. So Emperor Mingo's comment that perf needs to be runnable without guest client access (or guest host access) is the reality of data center VM.