I had this same issue with my connection servers. I had about 30 users on one of them, and less than 10 on another. I couldn't find any reason for it either, so I ended up opening a low priority case with VMware Support. They found the answer:
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Found the answer for you: It appears that users who require a password change and change it as they login to their View Desktop create a user profile on the Connection Server
http://social.technet.microsoft.com/Forums/windowsserver/en-US/eb56b301-feaa-4753-a70a-cd950bafa303/windows-2008-invokechangepassword-lots-of-profiles-in-cusers
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Thinking about this some more, this probably only affects organizations that run the View Client as an explorer shell replacement (we do this), effectively replacing the normal windows authentication. So basically, when a user's password is going to expire, the only interface they have to change it in is via the View Client. Apparently that change mechanism ends up creating an empty profile on the windows server itself?
From the article, it would be interesting to test changing the Allow log on locally option to see if it prevents the profile creation, or if it breaks password changes!