Why can’t you get a permanent crown til 18 ?

I never heard of that. I remember my friend breaking her tooth on a cookie in high school and she got a crown. How is a temporary crown supposed to last 2-3 years. I mean I’ve had my share of crowns at this point but I’m a little older. And the temps didn’t even wanna stay on half the time for the three weeks waiting for permanent. Then Heather makes it sound like it Ellie’s fault she has to have her wisdom teeth removed 🙄bad timing I guess now that Emma won’t be around as much