I'm not sure why I did it, honestly. I think I just wanted to do something nice. I also figured it would just be a nice gesture to "take care of the bill" so that everyone else wouldn't have to worry about it and could maybe relax and enjoy the rest of their evening without the possibility of them being concerned about how much money they had spent. I think on some level I felt guilty about other people spending money. And when I would buy someone a meal or buy them a few drinks I wouldn't want or expect anything out of it. To be honest, it made me a little uncomfortable if people made a big deal about it or even said anything more than "Thanks".
I've had times in my life when I've had extra money to spend and had times when money has been tight. And I know I've experienced occasions where money is tight and you go out for a meal with friends and spend a portion of the night feeling guilty that you're spending money. I think that when I had extra money, I just wanted to make sure that no one was feeling that way. I just wanted to give them the opportunity to enjoy the night, or enjoy lunch, or whatever it was we were doing.