I think expectations exist whether we like it or not, in every relationship. I think it's human nature to some extent.
What differs is whether they are reasonable expectations, and that is a completely different definition. (Although, to be fair, I agree with earthworm here - first we have to decide what "healthy" is...)
Expectations are based on known/past behavior, IMO. So when we talk of lowering or dropping expectations when dealing with our qualifiers it's another way of saying, "Make your expectations more reasonable".
Because of THEIR diminished ability to hold up their end, "reasonable" generally means extremely low or non-existent expectations altogether... otherwise we are fooling OURSELVES into expecting more than what they can actually deliver. They show us that by the lies, the disappearances, the manipulations & hidden agendas.
On the flip side, when someone shows you that they can meet & exceed your expectations consistently, it sets the bar for the future expectations you develop, based on the trust you build notch-by-notch along the way.
My non-addict boss is high-functioning-dysfunctional despite the lack of addiction in her world. She is positive to a fault & consistently sets her expectations way too high, trying to use it as a motivator to achieve said goal. Instead it backfires, she feels a negative reaction for not achieving something out of reach & it dominos into other areas of her self-esteem. But I cannot. get. her. to. see. this. In 5+ yrs of working together she has never achieved a goal on time because she sets her expectations too high, too soon, too vague... whatever. But she would very much consider herself "healthy".