How come google apps users cannot use google plus?

I don't even really know what being a google apps user means. Like I use google apps and I can use google plus.|||Google Apps has a guaranteed that their services would be error-prone and reliable. Google cannot yet be sure that Google+ would be available like that and they restrict it in order to protect themselves legally.|||Google Apps is a service that Google sells to businesses. It lets employees use Gmail's services for their @business.com email addresses (which is different than just forwarding your email), and it lets them use other services such as Groups and Docs internally (so only members of that company can see the docs or join the groups). If you have a Google account that was created through Google Apps, you can't join Google+ because it hasn't been activated for those business accounts. If you have a Google Account that you made yourself (for example, when you signed up for a Gmail account), then you can get a Google+ account, as soon as you get an invite to join.|||http://www.plus-google.co.cc/