Why are people so harsh and critical about someone’s art?

When someone asks what the think and some people can be so HARSH. Samsung it looks crappy some say it needs more which I understand, and some said, “I’ve seen better”.
I asked my cousins one time, but they thought about my art in they said, “No offense but your drawing looks like it’s drawn by a kindergartner. Hey you ASKED, I gave you an honest opinion.”
Ouch that hurt.
“It looks okay, but you can do so much better.”
“You call THIS art? This is pathetic. Plus your writing is crap and you write like seven year old. Learn to write better (I was 15).”
That really hurt me so bad. My friends one time said that my art looks great and fantastic BUT my best friends told me I can do a lot better and I need to it looks like I scribbled.
I said, “Well our friends said it looks fantastic and -“
My female best friend said, “They’re just saying that to make you feel better. As your best friends we’re going to be honest. It looks bad.”
My guy best friend said, “I mean just keep at it. We’re your best friends. We’re going to tell the truth.”
I don’t know if I want to be an artist because people are so critical about art. Even my art teacher said she didn’t like one of my drawings.