CC Commission would be built into ticket price I'd imagine as I believe they get charged the 2-3% for physical transactions, but yes, Anti-Fraud, Transaction Fees for online merchant accounts all valid reasons.
Something I'd also like to mention, the costs are far more likely to be more in line with reality that what Ticketek charge for concerts etc.
It's also possible they just eat the commission on CC Transactions at the POS because there'd be less of them, and the margins could sustain it. But the transaction fee is actually higher for CNP (Card Not Present) transactions so they may have opted not to simply absorb it for those.
To the OP: There's lots of possibilities really, and almost none of them involve them simply charging it because they're greedy.