Ask HN: Why has no one replaced Ticketmaster?

I constantly see people complaining about ticketmaster with scalping, nasty business tactics, broken interfaces, etc. and they get sued left and right after countless big events.

Yet even with all that, it seems no competitor has been able to reasonably get off the ground and poise a viable alternative. What gives? What's their moat/why do they have a monopoly?

There is a discussion on Hacker News, but feel free to comment here as well.