Firstly to the above - I 'assumed' you were saying these aspects of relationships you have viewed from the outside
are unhealthy and in unawareness based on your putting 'normal' in inverted commas
I do still say however, one cannot know the length and breadth and depth of any other person's experience from the outside.
With that said, what is YOUR monogamous relationship based on if it is indeed NOT based on give and take, needs being satisfied? Clearly, as Jen pointed out, we enjoy the company of this person, we can relate to them on some level and there is enthusiasm about seeing them.
But, what else is there that makes you say, THIS is the person I am in a monogamous relationship with as opposed to THIS person? Let's take sex COMPLETELY out of the equation for a second because often times we confuse this with "love". Why do you choose monogamy with THIS person as opposed to THIS person? I ask this question in a serious manner and would love to hear other's responses.
Recognising the length, breadth and depth of the connection to another person when it is not based on need or egoic fulfilment, or sex, comes down to a willingness to melt the barriers between us, and humanly - physically, materially we do this in an atmosphere of no fear and authenticity.
Where society and individuals over-pin their expectations upon one another, one feels the need or priority in acceptance to bend somewhat towards the 'socially acceptable', in some ways the sorts of behaviours and labelling etc that you mentioned earlier. The ways one introduces - relationally - another in terms of social acceptance and describing the relationship so as to inform the person being introduced as to the length-breadth-depth of the connection, within social constructs.
When two connect and their connection melts the socially constructed barriers between them the intimacy - the sharing of self/s brings us deeper into who we really are - love. As Neale Donald Walsch's 'god' says -
Love is that which is free, for freedom is the essence of what god is, and love is god expressed.
Love is the freedom to express the most joyous part of who you really are - the part that knows that you are one with every thing and every one. This is the truth of your being, and is the aspect of Self which you will most urgently and earnestly seek to experience.
This freedom to express the most joyous part of who you really are does notice the environments and relationships in which you are given length-breadth-depth in which to express that freedom.
If folks are uncomfortable in deep levels of authenticity and honesty - the highest forms of love, then it would be unloving to foist them into it, they would flail and react in fear to the lack of boundaries that conditions them to feel safe. Hence we have deep relationships and superficial relationships by all but silent agreement.
I don't actually think this has anything to do with exclusivity, or sex, it's more about agreements made and honesty about what the relationship serves in who we really are, and what it doesn't. Monogamy is a societal construct.
In example one can have deeply intimate platonic relationships, so deep that sexual partners unaware of the parameters of the relationship may become jealous of the intimacy shared. Now for me, one does not take anything away from the other so I am more likely to embrace, encourage and celebrate if a person has friends who love them deeply and provide a 'safe' environment for them to explore who they really are. Similarly in negotiating parameters of relationships my platonic relationships are 'off limits' as in: No I will not give up relating deeply with others in love in order to 'gain' love from someone or ease their baseless fears.
I am love, so no one can take love away from me, nor can they bestow it upon me, we can only create the space for each of us to be who we already are - love. I find that space with human friends, with my parrot friend (currently sitting on my shoulder having a nap while I type feeling uber-safe) and other species friends who are at my level of awareness of freedom and response ability in relating. I find that space in relationship with my self, with nature, with experience, with life.
We give ourself the freedom to be who we really are. In societal agreement we seek to find like partners.
In some ways the muddying of the waters where sex and commitment and vows etc are negotiated within societal expectations we kind of tighten the girth around our spontaneity and authenticity, but it need not be if we know who we truly are.
Authentic love is generous and kind and compassionate to self and other, so many of the 'agreements' are made in recognition and acceptance of fear as an experience, rather than in recognition of authentic love.
Albeit culturally exclusivity in sexual relations is kinda what monogamous has come to mean so I'm a little
as to what you are really looking for in answer.
The practice or state of being married to one person at a time.
The practice or state of having a sexual relationship with only one partner.
In my current relationship all I asked was that it be okay for me to be me.