What I don’t enjoy is when someone ropes me into doing something for them when it becomes clear that they had other intentions for the request. It’s the ulterior motive part that can have the opposite of the intended effect.
When you realize someone asked the favor not really because they needed it but because they thought it would be an opening to get you into conversation, you start wondering what their real motive is. In this case it may be benign enough, but it’s not a great way to start a conversation
Obviously tips are a factor, but it's common to see overtly friendly service in the US even for untipped positions (cashiers at Trader Joe's is one example that comes to mind). Being friendly in service positions in the US is just part of the culture. It's not universal of course, it depends on the specific business, but it is very common.
"Hi, can I ask you for a spot?" - hard to argue w/premise of ask and many people would be happy to assist you and see you achieve whatever goal you have for that lift.
I do both. But why I like a spotter: someone to coax another rep (or two) out of you. I'll coach them on that point in advance, too.