LOL - I do. Most of the time anyway. For a number of reasons already mentioned:

1) To set a good example for my kids.

2) To avoid a heapin' helpin' of crap from my wife.

3) I've broken more than one helmet. Never broken my head - well, severely anyhow. I guess that's open for debate.

4) I'm used to it from motorcycling.

5) I don't really take much comfort in the fact that my skull being softer than my helmet will cushion my neck. But then I have a pretty hard head.

6) You really SHOULD wear a helmet when driving a car. Talk about a dangerous activity! That's why I ride a bike.....