That's interesting. We live in Missouri and my kids have been able to get permits on their 15th birthdays.
As for the desire to drive young, that's a lot more about differences in kids' personalities than anything else. 2 of our 3 kids couldn't wait. The other had to be dragged into it and finally got his license a few days shy of needing to start commuting to a college 30 minutes away at age 18.
Some of the kids' friends have delayed because the parents did not want to pay the higher insurance premiums. My son's 20 year old friend still doesn't have one.
It's really all over the place.
After a variety of experiences though, I do find myself advocating for sooner rather than later so you can supervise their driving experience longer before sending them out in the world. It was way too stressful for all of us watching the 18 year old head out on his own with relatively little experience.
You're right - personality plays a large role. So does living in a town of less than 10,000 in the heart of the Missouri Ozarks! Where I'm from, a lot of kids were driving on the farm since they were old enough to see over the steering wheel, and the rest of us just wanted a way to escape

And at the time I got my license,many years ago, 15 and a half was the age for permits (the graduated license law was not in effect at that time in Missouri, which now allows for a beginner to be 15). Everyone had a "when I turn 15.5" countdown, and I marked that magical August day on the calendar like it was second Christmas, passed my written permit test...then didn't end up getting my license until the May after I turned 16 in February, because I had to take driver's ed second semester (and my mom refused to drive with me...well, she did once because my driver's ed teacher told the parents to let us practice, and it ended with me crying hysterically in a grocery store parking lot because she wouldn't stop shouting at me).
We no longer live in Missouri, and the beginning age where we are now is 14 - that blows my mind (we won't be letting the kids start then!).
I can imagine the stress of watching your 18 year old drive away on his commute. I do admire people being self-aware enough to know when they're ready to take certain steps in life, but I agree with you on starting sooner and having an opportunity to help your child build stronger skills before they head off on their own. I tell my boys, you don't HAVE TO drive, but you have to KNOW HOW to drive. (My mother wouldn't allow me to be in the car with any driving friends before having a license of my own. At the time, it was a huge pain, but I always understood why

) I'm curious to see how they actually feel when the time comes, they might want to wait, too.
Driving early was my expected norm...
That's why things like this are fascinating - we all have different life experiences, different perceptions, and different ideas of what constitutes "normal". It's interesting to see how things vary around the country (even in different places in the same state!), and how different families approach the subject.