How come some people don't like telling others where they get their clothes?

My cousin had a really cool bling bling necklace. I asked where he got it from. He was like, "Uh...(chuckles)".
I'm like, "What?"
They didn't respond. That was rude. Then his mom (my oldest cousin) said, "Well not a lot of people like to say where they get their clothes from. Plus they like having their own style and they don't like people copying them."
I guess I get it. I understand but not answering is very rude.