But I don't think every single family will be saying to their child 'you should feel grateful, you owe us',

While this happens in an insane amount of cases, you are right it doesnt happen in every case, what does happen though is that the wider society does that. Adoptees who do not have good relationships with their adoptive parents get a lot of shit from random people who tell them regardless of how good or bad their adoptive parents were they should still be grateful. (and we also get told all the time that we should be great full we weren't aborted)

I actually think all people have an attachment to blood, its not actually about the blood, its about not experiencing genetic mirroring, not knowing your medical history etc. also I don't think the land thing is relevant. The land I feel connected to has nothing to do with my blood family its where I grew up with my adoptive family