The thing is that it used to have an installer that was removed at some point. It was a simple menu that just covered the basics and would leave you with a working system withing minutes. I don't know why it was ever removed.
It really depends on what you're doing. If you're working on multiple projects that depend on other services to be running then it probably helps to use Vagrant. If you just need libs virtualenv is enough.
There isn't really a reason not to use Virtualenv wrapper, but there is also not really a reason to use it. Activating it is rather simple, so I just didn't really want to add something else to the installation (that would make it slightly more complex and slower). However, take a look at the development role[0], it actually activates the Virtualenv on login.
If you're going to be logging into the production machines (where the development role does not make (total) sense to have) you may want to install it, or turn off everything in the development role[1] except virtualenv activation and add it to those machines.
In short, I'm not against it, I just think it's not needed since the development role makes it redundant to have.