Do you really need a car?

Now I know a lot of people have no other way of getting to work and stuff, but I think there are a lot of people clogging the roads every day that don't really need to be. There's a girl at work who has started driving in from Finglas every day, we work in the city centre, and is quite happy to sit in ridiculous traffic for an hour or more every morning. Single occupancy too. This isn't an isolated case in my work either, quite a few people do it. I used to live out that way and bus took about 30 mins max into town even at rush hour.
She earns way less than me and must be paying 1000s in insurance. Why are people so adamant to be driving? I have use of a family car when I need it, which I may use once every week or two to go for a spin but that's about all. I usually regret it as Saturday and Sunday afternoons can sometimes be really clogged on the roads with arseholes (like me) driving around aimlessly.
I cycle to work most days, and nearly all the cars seem to only have one person in them. I remember talking to a girl online a few months ago who drove into town every morning from Artane ffs! That's about 6km, you could walk it in less than an hour. She said she didn't mind sitting in the traffic for ages because it was nice and warm.
This kind of thing almost makes me favour a congestion charge in Dublin, if the money was put to good use to get the roads flowing.
So could you do without your car? And how are people willing to pay these mental insurance prices?