I wouldn't call this greed. They are covering their ass... i.e. if your gf gets pissed and leaves you they don't want the hassle of changing account information (which stems from their account selling policy). It makes sense that every adult should have their own account. Period. Plus, those are the rules, so if you don't want to abide by them then there are plenty of other entertainment options.

Children are different since they are under your care... you are making their decisions for them. When they become of age they would need to purchase their own account too.