The thing I don't like about the risk management argument is that aren't these performances usually put on by major labels? Or is it the venue that is taking the risk?

If it is a large label that puts it on, they already have a "diverse portfolio" in some sense, so if one show bombs they can rely on others to balance it out. Even if they do need to manage risk, surely there is a more efficient way to do it?

Maybe you're right and it is the result of benevolence on the part of the artist.