I've been greatly enjoying the food at our two local food trucks (Chef Tai & Madden's). Excellent food, generous portions, good price. My husband and I end up eating at one of their trucks atleast once a week 
My question is about tipping. You can pay by credit card, and the receipt always has a spot for tips. I don't usually leave a tip. But last time, as I was signing my receipt, I could see some of the other signed recipts on the table and found that a lot of people leave tips.
What is the norm for food trucks? I don't feel that they're providing a service I should tip for ... am I missing something???

My question is about tipping. You can pay by credit card, and the receipt always has a spot for tips. I don't usually leave a tip. But last time, as I was signing my receipt, I could see some of the other signed recipts on the table and found that a lot of people leave tips.
What is the norm for food trucks? I don't feel that they're providing a service I should tip for ... am I missing something???