I don't think dogs work to please people. I'm not so sure they are capable of the empathy needed to know they are making you feel happy. They can obviously see your behavior change when you are happy, and they might like that, but I don't think they can truly understand how you feel. I do think some dogs find praise and petting rewarding, and some find you getting excited rewarding. I also think some dogs truly enjoy working, they find solving problems fun and enjoy working with people, whatever the task, they find the work itself fun. For instance Tucker was taught to high five, we ask him to high five all of the time, he hasn't gotten a food reward for high fiving in over a year, the most he gets is petting but usually just cheering and good boy! Tucker LIKES high fiving, he finds the action and the excitement around the action rewarding. He also doesn't see it as a lot of work, it's super easy for him to do, he doesn't even have to get up. So there's really no down side to do it. It's also not something that is ever used to prevent him from getting his way like a sit or down or come might be. It's not like he sees a dog he wants to go see and I start telling him to high five, I'd tell him to sit. High five is always low pressure, never difficult to follow. If you had a dog who felt that way about every command or actually enjoyed challenges you'd have one easy to motivate dog.