We may be the exception, although it’s only been 13 years so far. Her and I didn’t ever combine our finances other than to open a joint savings account, so it’s never been a discussion of “we need to partition our finances”, it’s just never been a discussion of “we need to collapse our finances into a single pot”.
We do have a significant income disparity (on our taxes I believe it was about 3:1 for me this year), and navigate it mostly by just having an asymmetric set of financial responsibilities. We’re both responsible for our own individual expenses (e.g. cell phone bill, car insurance, credit card debt). She covers the mortgage for our modest house, I cover pretty much everything else (house and cabin insurance, property tax, car insurance for our shared POS construction-hauler van, natural gas, electricity, water/sewer, charitable donations, etc). I know what the mortgage costs, she probably doesn’t know exactly what most of the stuff I pay for costs but I’d be open with her if she was curious.
After all of the expenses are covered, we’re pretty much free to do what we want with what’s left over without consulting with the other person. We’re both also, I guess, sufficiently responsible that it’s a rare situation to run low. We’ve had a few unexpected expenses over the years that left the joint account in a bit of an ugly place but refilled it over the next few months and lived a little lean to make sure the emergency fund was there.
For COVID, her monthly income was reduced to almost zero. We’re in Canada, so she had CERB ($2k monthly). I topped up the joint account and told her she was welcome to take what she needed. She did transfer maybe $1k a few times to cover a few things, but mostly was self sufficient.
I dunno! Maybe it’s not a situation for everyone but it’s been super smooth. When we first started dating and moved in together, I was a grad student with a paltry scholarship, but our expenses were quite low as well. She got by and covered a few more things than I did, and now it’s going the opposite way and there’s no resentment or anything as far as I can tell. We’re both pretty good about sharing when we’re feeling something’s out of balance, so I suspect I’d know about it if she didn’t feel like I was pulling my weight.