Do you ever pay it forward?

My BFF& I went to lunch together today. As we were eating, a couple of guys at the table behind us got up to leave. As they passed our table, one of them picked up our tab & said “I’d love to buy your lunch today” & walked up to the cash register to pay our bill. My friend was just beside herself as this was the first time this has ever happened to her. As we got up to leave, we walked past an elderly couple’s table & she picked up their tab saying “I’d love to buy your lunch today”. As I walked by after her, the elderly lady was in tears because she couldn’t believe that anyone could be so nice as to buy their lunch. I do this frequently kind of when the mood hits. I’ll be looking around the room & suddenly I see someone & my brain thinks “I feel like treating them to lunch” so I do. Do you every just suddenly decide for whatever reason to buy someone’s meal???