The price tickets sell for will be higher if scalping exists. Demand increases for 2 reasons:

1 - I’m more likely to buy a ticket or pay a higher price if there’s a chance of turning a profit if I can’t go.

2 - Speculators are more likely to buy unused inventory if they can turn a profit. This increases total tickets sold. (Scalpers get paid for taking risk)

I’m not defending this. I’ve given up on concerts for my favorite larger bands due to sticker shock.