Why are children 10,000% nicer than fully grown adults (most of the time)

Okay, so where I work, customers or either old people in their 60s+ or young children. No in between lol.

And I want to say about 99.99% of the time, the children are WAY nicer and more understanding than adults.

Just yesterday, there was a little kid with (I'm guessing was) her grandad. And when i went to put her milkshake down, a bit of it dropped/spilled down the sides. It didn't go everywhere, just a few drops on the table. I apologised a bunch, and went go go get napkins, because I've been yelled at for stuff like that before lol (at work, and when i was younger). And the old guy was like "it's okay love, just clean it up. It didn't make a huge mess". When i came back and wiped it up, I apologised again, and the little kid looks at me and goes "there's no need to say sorry, people make mistakes, it's okay. You didn't do it on purpose. Thank you." (I had to try not to cry at the start of my 9am shift lol.) I thanked her, and said how sweet that was. And I told her grandad that she had better manners and was kinder than 90% of the adults that i serve, and he seemed kind of shocked.

Like how on earth can an fricken 8 year old, be more understanding, and have better emotional regulation skills than a fully grown adult?!?!?! Like, how?!?!?!!

And it's happend before where, kids will say "may I please have" or "thank you". And adults won't even look up from their phones, and just say random drinks and food at me. Like!??!?!!

And, sometimes kids can be bit crappy (I had a bunch of 12 year old boys call me bitch for not giving them free food lol) but like, percentage wise, the adults are WAY worse. Yelling at you in the middle of a rush, complaining about the stupidest things humanly possible, not even acknowledging you.

Idk if anyone else has noticed/experienced this, but I've been picking up on it for a while, and it's just SO confusing and shocking to me!!!