@Hawaii_Jake – With my limited experience in ticket-selling, centered entirely around the local heavy metal scene in Tampa, I can say that in some cases at least it’s a matter of assuring that the venue brings in the minimum amount of money necessary to pay the entertainment.
Take this example:
The Fluffy Kitties band (not a real band that I’m aware of) has been invited to appear for a Friday night show. They have a $2000 demand. A contract is signed stating that the band will get the two grand, and if ticket sales don’t add up to that amount, the venue is on the hook to pay that out of pocket.
The venue advertises tickets at $15 each, or $20 the day of show. If 134 people pre-pay, awesome! Fluffy Kitties gets their money, and everything the bar takes in at the door is profit/split among the openers/whatever.
And if Fluffy Kitties doesn’t have the draw to get the minimum 134 paid goers, the venue can cancel the show and refund their money, cutting their losses for the advertising without having to pay the required demand.
If the price is the same in the two months leading up as the day of the show, there’s no incentive to pre-pay, and the venue can be out $2,000 when Fluffy Kitties’ three biggest fans – and no one else – shows up.