Comparative advantage is the name of the game. My parents have been doing that for years, even when my mom ends up with some manly work (tall house + lots of Christmas lights) and my dad ends up with some non-manly work. It works pretty well for them.
They even optimized which kid helps them, I worked better with my mom (I was all about getting a list of chores and powering through them when I had time, and so is she), so I ended up working with her for the weekly chores. Shutting up and getting stuff done really does make one happy.
My wife and I just assign each job to whichever of us is less annoyed by having to do it, and somehow it all seems to balance out. She cleans the bathrooms and does the laundry, I sweep and vacuum and take out the trash, she makes the coffee in the morning and I turn off the lights at night. We certainly aim to be equal partners in our marriage, but instead of tallying everything up for some perfectly fair 50/50 division, we try to embrace our differences and specialize in what we're good at.
Sometimes the breakdown does look disturbingly similar to the old traditional gender roles, but sometimes it really doesn't - I do the mending, for example, and she takes the car in for service. I'm sure we are both influenced by the traditional sexism of the societies we grew up in, but whatever the reasons for our choices, each of us pretty much gets to do what we think of as the easy or inconsequential chores while our partner tackles the nasty, time-consuming, or obnoxious ones.
> Sometimes the breakdown does look disturbingly similar to
> the old traditional gender roles
That seems somewhat inevitable. A lot of those gender roles are there precisely for comparative advantage and "do the thing that annoys you less" reasons. It just happens that statistically fewer men are annoyed by trash (e.g. they never get pregnant, so don't have months-long periods when they just can't deal with it at all), women are better at taking care of infants (e.g. can often feed them more easiy), and so forth. On average, etc. ;)
The smell is part of it. For some women also the sight, or even just the thought of either one. On average, pregnant women tend to react much more strongly to anything rotten or possibly-rotten; the details will tend to vary from person to person, of course.
They even optimized which kid helps them, I worked better with my mom (I was all about getting a list of chores and powering through them when I had time, and so is she), so I ended up working with her for the weekly chores. Shutting up and getting stuff done really does make one happy.