I can personally say that every time I've traded with a bank I've absolutely thought about it from the perspective of them taking a view contrary to mine. It would be bizarre if they thought that it was a good time/price to buy and instead they sold it to me.

I guess I think that every time I've given someone money it's because they're stronger (smarter/better connected/etc.) than me or because they're willing to do something that I don't want to do or because we value things differently. The last case might be the result of different utility functions or might just be the result of a mistake.

It seems like in any other circumstance there wouldn't really be a reason for me to give money.

I'll give money to a cobbler because they're stronger than me in the sense that I physically can't make shoes as well as they can. I'll give money to my house cleaner because they're willing to clean my apartment and I'm not.