We should have to apologize to them when they hand us our meal, that should be the "basic social interaction".
Well, it's not.
If "living your life" involves being rude to people and ignoring even the most basic social courtesies, you're an asshole. Part of the service people pay for when they go anywhere is not dealing with rude employees, and yes ignoring basic social courtesies is rude. If you're in Europe you get to have the European social courtesies of minimal interaction, no small talk, etc. If you're in North America you don't get that, sorry.
Further it is rude in no part of the world to not be cheerful, and the fact that you require this of people who are paid unlivable wages shows a distinct lack of compassion or empathy.
They’ll smile when you pay them what they’re worth.
My point, and I think @coldtea's point, is that if you basically ignore customers, you're rude and shouldn't be in a customer service position. I grew up in the northeast US and it was rare to have any customer service interaction where you received no greeting, no thank you, nothing - precisely because it's rude, and most people aren't.
You think these people should choose homelessness because they don’t want to cheerfully work for slave wages?
That’s callous and hateful.
In the case of Cold Stone Creamery though I agree, those kids should not have to sing for tips.