What about shows where the number of people who want to buy tickets is about the same as the number of tickets that are available?
Without scalping, the band sells tickets for $X and nearly everyone who wants to go is able to buy a ticket for $X.
With scalping, the band sells tickets for $X, the scalpers buy a large fraction of them or even all of them for $X each, and then sells them for much more than $X each.
This doesn't let people go who otherwise would not have been able to. It just makes them all pay more to do so.
If demand is comparable to supply at the price at which the tickets were initially purchased by scalpers, then the fair market value on the secondary market would be about the same as the initial price, at which point the scalpers would have lost money on the deal (after accounting for secondary market fees), and customers would end up paying about the same price as they would have if they had purchased them directly from the venue/promoter.
Without scalping, the band sells tickets for $X and nearly everyone who wants to go is able to buy a ticket for $X.
With scalping, the band sells tickets for $X, the scalpers buy a large fraction of them or even all of them for $X each, and then sells them for much more than $X each.
This doesn't let people go who otherwise would not have been able to. It just makes them all pay more to do so.