Why isn't my Apple ID associated with my Macbook?

I've just disassociated a device from my Apple ID (an iPad that I no longer have) and I noticed that my Macbook Pro isn't 'associated' with my Apple ID, which probably explains why I don't see all my Apps and stuff when I open iTunes on my Macbook, and why I can't sync my Calendar from my Mac to my Macbook.

I have the same Apple ID login and password on both devices so I would assume that they should be connected, or associated.

It looks like only my Mac and my iPhone are 'associated' with this ID and account.

Can anyone help me figure this out?

Thanks.