things I don't understand - Am I invisible or do you just not want to wait your turn?

So I was in a food place today getting a sandwich. The person at the counter was making the sandwich for me, and she was the only employee that was visible, and there were no other customers waiting to be helped. She was almost half-way done with making my sandwich when another customer walked in. He walked around me, went up to the counter to about where she was on the other side of the glass, and he said he wanted to buy a soda, and he had his money out.

Ummm, ok, dude, she's IN THE MIDDLE OF MAKING MY SANDWICH. She's got plastic gloves on to make the sandwich, she's busy, there's no one else to help you, and I was already here when you walked in. OK, so you only want a soda, which mostly just involves her giving you a cup and taking your money since you'd be filling the cup yourself. I'm getting a sandwich that takes more time. But did you expect that she'd stop what she was doing for me, take her gloves off, take the money from you and ring you up and hand you a cup AND THEN go back to making my sandwich?

To her credit, she looked at him and said she'd be with him in a couple minutes. She finished making my sandwich, rang me up and took my money, and then when she was done with me, she asked him what size soda he wanted.

So, did he just think she was standing there doing nothing and somehow, I was just invisible to him, which is why he just went up to her and told her what he wanted, even though she was busy already helping another customer? Or did he think that since all he wanted was a soda, he would get to cut in front of me to get her to help him? I've seen people do that where they're interrupting to ask a question, which I still think is weird since it's not their turn yet, but to actually expect her to stop helping someone else to help him instead?

I don't get it.