Why is speed dating usually executed in the slower form of 1:1 speed dating instead of 2:2?

I'm with you, and I could do that.  But what would happen, in reality, is that two of us would like the same person.  And that's too public. And also in my experience, I'm the one that gets rejected on a quick first pass in a room full of "normal" men.  I am most definitely an acquired taste.  So it would be twice the pain in half the time. You want me to pay money to do this why? So your theory would work for a roomful of mathematicians, perhaps physicists ? , and almost certainly, most gatherings of Mensans.  Outside of these few pre-selected groups, you would have trouble assembling a sufficiently large sample set.

If I understand the premise, 2 guys sit down with 2 girls to get acquainted.  Is that right?  Or, based on a comment after Karen Tiede's answer, if 60 guys and 40 girls show up, it would be groups of 3 guys and 2 girls.  Sound like a 5th grade math problem:  Jim can paint a 30 foot fence an 2 hours and Bob can paint  a 50 foot fence in 3 hours.  How long will Jim and Bob take to get acquainted with Rebecca, Robin, and a bottle of Chardonnay?  I bet Joshua and I would be competing to talk to Karen and both girls would get bored listening to us show off.  (I don't have any specific Karen or Joshua in mind, of course.) I mean, scale it up a little and you have the usual party.  What do you do at a party?  I spend the whole night looking for one person worth a private conversation.  Some people will do better at a party, but some people will do better 1:1 speed dating.  A 1:1 speed dating event with 20-30 people might be the optimum between the extremes of just two people stranded on a desert island or all 7 billion of us in a really big room.