We used to have one car and a baby. H road his bike or bussed to work. I drove to work (~17 miles).
We only needed the second car occasionally and when that happened we rented a car for the day. This worked ok (they came and picked you up from the house and the price was reasonable). It was a pain though because it took forever. Now with the prevalence of Uber and car-share services, I am sure that would work.
The big thing is that carseats are a pain in the ass. No way would I be Ubering with little kids. Even now that they are in booster seats what the fuck do you do with the seats while you are at whereever you are? Carry them along with you? lol for days. No.
Now we live in a smaller town with no bus, no car rental places, etc. It is bike or nothing and it is not bike friendly. The kids are right on the edge of being ok to stay home if I need to run H into work. My definition of not fun= getting little kids into snow gear at 7 am to drive dad to work, then repeating right in the middle of dinner prep time.
So, long story short, it depends on how much that at-home parent wants to get out and about, and how much is in walking/biking range. I personally would go bonkers just staying home all day every day while H works. So I would be having to run him to work 3 days a week to have the car during the day, which sucks. For someone happy at home all day it is much easier.
And since our second car is old, cheap, and no longer depreciating, eh, it isn't worth getting rid of. Once the kids are older it will change to them needing to be driven more places, and you'll have a whole 'nother set of issues.
That said, it is still my goal to eventually get down to one car. It won't happen in our current town though, and it probably won't happen as long as we have kids in the house.