My grandparents on my Dad's side of the family only had one car their whole life. They worked fairly close to each other and carpooled in. They both retired around the same time as well. Never seemed to bother them, having only one car.
Now on my Mom's side of the family, they always had a car and a truck. Grandmom drove the car and Granddad, who worked on a farm, used the truck. In the late 70's when inflation started running rampant, and cars were getting too complicated to work on, Granddad bought an additional car, a 1953 DeSoto Firedome, to use as a spare car. I think he did it to keep the miles off their '72 Impala, but as time went by, Granddad just lost interest in that DeSoto. It finally sat too long and wouldn't start anymore, and right around the time I was nearing 16 and showed an interest in it, he suddenly decided to sell it!
In 1976, Granddad bought a big GMC 3/4 ton crew cab truck, with the intent of using it for camping, but it was really too unweildy to drive around for daily use. So they also ended up landing a used 1972 Chevy LUV around that time to beat around in.
I have a co-worker whose mother remarried after her father's death, and they tried to go down to one car. But then her mother ended up hating the loss of independence that came with it, and having to depend on her new husband. I think that he did it as a ploy to control her...from what I've heard in conversation he's the type to pull something like that. After a few months though, they ended up getting a second vehicle.
I guess some couples can make it on one car, but it just depends on the situation. As for me, I have 7! But 4 of them are toys, one of them really needs to be sold for parts, hauled off to the junkyard, or something, and then I have a daily driver car and a truck. And they're all bought and paid for, and I think insurance for the lot of them is only about $1300 per year.