There are lots of different variables that influence adherence, including but not limited to:

- expected or actual efficacy

- regimen complexity

- knowledge, commitment, and ability

- doctor-patient relationship

My understanding is that with HIV a lot of money has been spent on actually implementing the adherence research in order to reduce the spread of the disease, whereas for most other diseases no one really cares. I think getting diagnosed with HIV also encourages some people to grow up a little bit in a way that getting diagnosed with high blood pressure or whatever doesn't, though maybe less so now that infection vectors are changing.

It might also be worth noting that adherence with HIV medication is also motivated by simple fear: if you don't take it, you will die. Painfully, from secondary infection.

Diabetes (type 2) and cardiac disease are scenarios where people can still kid themselves to a certain extent.