As mentioned previously, people are usually not themselves on a first date, especially a blind date; or at least you don't really get to know the real person usually. Thus hanging out provides a setting in the which you can get to know people without the pressure of “Do you want to marry this person?” looming over your head as it does in a dating relationship in today’s society. Some people feel like you can’t really get to know someone by just hanging out. I submit that that is up to each individual. If you just sit and watch TV, then sure you will never get to know someone, but I think you can learn as much talking with someone in a group setting, as in a one-on-one dating situation, if that is your goal. Who hasn't been on a date that was much pretty much a long sequence of awkward silences?
Obviously dating should be the ultimate goal of group activities. Use them as an opportunity to find out if you'd like to date someone and to meet new people i.e. friend of a friend. There are some things that you only get on a date. Especially with some girls who always seem to have tons of guys surrounding them, people calling on the phone, etc. You pretty much have to go out with them just to get to talk to them for more than a minute w/o being interrupted. And obviously, your odds of getting some action are MUCH higher after a date. ;) Maybe I should look into dating more.