By this I mean, that if a couple are married or are living together with a similar level commitment, that any income disparity between the couple should not be glaringly obvious? Or that (excluding the very rich and massive inheritances), they should have a similar enough disposable income that they could do / buy the same things?
I do know there are really good reasons why this isn't the case for some families (blended families, maintenance payments, aforementioned wealthy etc.), but for the rest, surely this is the norm?
My experience growing up was that both my parents had access to whatever they needed. Sometimes it wasn't enough, but when there was surplus, if dad wanted a gadget or mum wanted a handbag they're quite traditional then they got it. This is also how myself and DP work.
From what I see with friends and close family this isn't the norm. I have so many female friends who have gone part time to look after DC and can't afford this, or that, but have DP buying £2k laptops, £1k cameras. One was asking her DP for a hair dye and cut for her birthday, when said DP is decked out in designer (for work 
).
I have other friends though where I really want to scream - independence is the ability to look after yourself and any dependants if and when you need to, not the ability to pay 50% of the bills regardless. They make sacrifices they don't even register then respond to invites or buy things for themselves based on their income rather than the income they have facilitated.
FWIW I lose out by our arrangement and I have no DC so I have no axe to grind. I just think that a family ought to have the same standard of living. I do and likely always will earn more than DP unless he builds a start-up, but I couldn't not share, because we support each other 100%.