I'll do you one better: explain how requiring an ID prevents ticket scalping.
To be honest, I couldn't care less about scalpers. The limit on ticket purchases already do a pretty good job preventing the "I'm going to buy ALL the tickets and resale them for 10% more" business plan. I see no reason a private individual shouldn't be able to resale their ticket for any amount they think they can get for it.
Requiring ID prevents scalping because you have to be the person who paid for the ticket in order to use it.
IIRC my last TicketMaster ticket was transferable - there was a webpage where I could change the name. But presumably if one credit card/IP address transferred the majority of its tickets, you could say with some confidence that that person is a scalper and shut them down.
The limit on purchases is reasonably effective, though.
To be honest, I couldn't care less about scalpers. The limit on ticket purchases already do a pretty good job preventing the "I'm going to buy ALL the tickets and resale them for 10% more" business plan. I see no reason a private individual shouldn't be able to resale their ticket for any amount they think they can get for it.