Because many of those videos won't be replayed over and over again. It's like recording fireworks. Almost pointless. You may as well just enjoy the concert (edit: without videotaping it.)
The tape recording, though, you bet it was enjoyed countless of times!
Yeah, and you can tell just by the look on his face that this is serious business. He's just got to hope nothing going wrong while it's recording. I'd be so nervous about something breaking in the machine!
In communist Poland some things you could only hear and record live, because that was harder for censors to stop. Even then there were censors backstage crossing out forbidden lyrics from the sets. However they would often get ignored as an act of defiance, especially at punk rock concerts.
But there was no way to officialy distribute these kinds of materials and doing so could land you in jail.
So unless you had some kind of underground source, your best bet would be to go to a concert and record it.