Does the steam version of blender install Python automatically? I'm not really having any problems.
I've just recently downloaded "make human".
on the download page it says it needs Python installed to work.
I haven't installed Python but it seems to work anyway.
And I'm assuming that's because Python must be bundled with the steam version of Blender.  because the version of blender I have was installed through the steam client.
If that wasn't already apparent.
Python is bundled with all versions of Blender, since 2.5 onwards. Many aspects of the UI are declared in python and it is therefor an integral part of the UI system (shipping without would be a world of hurt).

According to Make Human docs the add-on comes with its own version of Python ( 2.7 ). 


  (...) there is a bundled python inside the build zips (...)


This means you have at least two versions of python on your machine, one that Blender uses and one that Make Human uses, that's OK.