Saying that they maintain ticket availability for longer, it's a zero-sum game. The only reason those tickets are around longer than they otherwise would be, is because alternate purchasers were unable to get them.
Put another way, if 100 tickets at $50 sell out in a day, and scalped at $500 sell out in a month, yes, the same amount of tickets is sold. But 'ticket availability lasting for a month' is only there because the scalper has removed the ticket availability for the $50 purchasers.
Economic theory say that this isn't true. They should sell out at similar speed regardless of reselling happening or not.
And from personal experience: efficient markets are better than inefficient markets. I've seen quite a few inefficient markets and they're ... well they're stupid. They impose ridiculous costs (like having to F5 continuously so you can "deal" with the shortage, but that's quite a trivial one).
And yes, scalpers make the market more efficient.
The presence or absence of scalpers does not change the basic problem : not enough spaces for everyone who wants to go. That cannot be solved by introducing rules against scalpers. In fact, the opposite is true. Seriously, the opposite approach would likely improve matters far more : create a large-scale scalping company that would pre-purchase large amounts of tickets as an investment and resell them later. The presence of this company would massively improve ticket availability by enabling and incentivizing artists to make more spaces available, and this would make everyone's life better.