It's a moving target. Forging tickets has gotten easier and easier, and as tickets get more expensive it becomes more and more lucrative. Law enforcement is generally not helpful for this sort of petty larceny so they are looking for structural ways to prevent it.

In past eras they used holograms and watermarks and special papers in an attempt to prevent forgery but these methods keep getting challenged by an ever more sophisticated criminal element. Moving into cryptographically secure methods is the last barrier here.

They could also rely on the state to match identities to tickets, but this approach does not scale and is frankly undesirable for the majority of people anyway.

Decades upon decades of holograms and watermarks on tickets to make them unforgeable. But it keeps getting easier to forge them. Meanwhile ticket prices keep increasing (venue space is one of the last things that's truly scarce) and the incentives for forgery keep increasing.

Even if we could make them truly unforgeable, people generally want electronically transferrable tickets. How do you propose to do this?