Scalpers/brokers aren't economic parasites, they provide a function to artists and promoters by offloading risk, and they also provide liquidity to fans.
If if it comes down to selling out 50% of a venue immediately and the other 50% over the next 2-3 months, or selling out 100% of a venue in one day, I imagine most promoters and artists would like that money now so they can utilize it. Brokers trade use of money over time for risk. Sometimes they make money, sometimes they lose money because it's overbought, they misjudged the market, or more supply was provided (a date added at that location). For example, see here[1], where resale tickets are under the cost of primary market tickets, $36.50 instead of $39.50, and that's before Ticketmaster/Stubhub takes 5-10% of the sale price from the seller. On Stubhub[2], the same tickets are going for $27.
1: https://concerts1.livenation.com/event/000054C6CF1B8160
2: https://www.stubhub.com/the-damned-tickets-the-damned-new-yo...