You can't resell a plane ticket. You can get a credit or cancel the purchase depending on the airline's terms. But there is no secondary market in plane tickets. If you show up at the airport and your ID doesn't match the name on the ticket, the ticket is invalid.

That is a (relatively) new thing, however- at least in the US. Prior to the September 11th security reforms there no ID checks against tickets, and you could resell them. This was so commonplace that one US airline (People's Express) back in the 1980's did all their tickets paid in cash after you boarded. They had no idea who would be on a flight at all until the boarding started!

(You can see this in the spoof movie Airplane II: The Sequel from 1982, where our hero boards the Lunar Shuttle buying a ticket from a scalper.)

So this policy is younger than Google.

You can also buy plane tickets from a number of providers.

Venues don't want to be checking all that at their gates plus they don't want to prevent scalping it's only really the artists and fans who are anti scalping the rest of the parties in the pipeline loooove scalpers.