Why do parents laugh at their kids dreams?

I'm currently a high school student who aims to become a physicist. I have high grades, and was accepted to various science programs for my grade 12 year. I took the AP Chemistry and Physics exam and got a level 5 in both of them. Though I have very high grades, whenever family comes over and I tell them i want to be a physicist, or a software engineer, they laugh. Like today for example. My Uncle came over, and asked what i wanted to become in the future. When I told him that i wanted to become a physicist, my mom started laughing. When i told him i was going to go for McGill university and apply to princeton, my mother started laughing again. It hurt a lot. It's not like I'm averaging a 70% with mixed courses and making wild claims. I'm averaging a 95% and took a lot of AP Courses, and Enriched courses and she still laughs... everytime. Idk why she does it. She doesn't even have a high school education. Does this happen to other people too? Thank you for your insight