On the train

As I got onto the train, I see three empty seats next to an old lady. Like so:

Old lady - Empty seat - Empty seat - Empty seat

Two school boys, pre-pubescent, entered one step before me. They looked at the empty seats, then looked at me. First boy sat down, then signaled second boy to sit next to him.

Old lady - Empty seat - First boy - Empty seat

Second boy looked at me. I was standing next to the Empty seat furthest away from the old lady. I said "you sit la", he said, blushing, "no, no". I said, "sit la!" "no, no, you sit". Finally I said, "you sit here, I sit there, okay?" I sat next to the old lady, and he sat next to his friend.

Old lady - Me - First boy - Second boy

Took me a while to figure it out. He didn't want to sit next to the old girl, and he thought I wanted the seat that he wanted.

At the optical shop

One of the plastic studs attached to the clasp on my glasses have been broken for months. Today I took it into an optical shop and asked if they could replace it. The man at the shop said they don't have an exact replacement but could change both the studs for $20. So I said okay. It took him a couple of minutes. He handed me my now repaired glasses, and I tried them on. They are perfect. I thanked him, and pulled out $20 from my wallet. He took the bills. He thanked me and said bye please come again if you have other optical needs. I said sure. I looked at him. He looked at me. Is he going to give me a receipt for that? I thought to myself. Still, he wasn't moving. He was waiting for me to leave the shop. So I left the shop.

Why didn't he offer me a receipt? Is it because he's pocketed that $20? If so, why didn't any of his colleagues say anything? Do they do this all the time? This time it's your turn to pocket the small change, next time it's me. Is $20 too much to pay for two little plastic studs? Should I have asked for a receipt? Why didn't I say anything?