In addition to what everybody else has said, I will add one more thing:

They don't go down when there's a big ticket sale. If you've ever used these alternative ticket sites, they will struggle under the load.

The reason it is hard is because there is a flood of people all hammering your site at once, all doing credit card transactions. There's bots. There's people hitting refresh constantly.

They are lame for a lot of reasons, but they don't suck in this department. And I imagine that is important for a lot of people.