I always felt a bit sad that it wasn't more normal for 'my crowd' to have scooters. I would've loved a scooter.
Now when those turned 18.. that's a different story, it did not take them very long before the driver license was there.
When I look at my nieces/nephews now, then it is mostly still the same story. Except that indeed the number of mopeds is higher, but still under 50%.
Grocery shopping is often less than 5 kilometers, but me and my neighbours often use the car for that (eventhough often it could be done by bike).
I think the biggest reason is purely cultural. It is normal (almost expected) that kids and teenagers go to school, sport and clubs by bike. You grow up riding a bike and it is your first real "liberation" from depending on your parents for everything.
It kinda represents freedom to go where you want to go before coming of age and being allowed to drive a car. (The minimum age to get your driving license used to be 18, though recently you can get a "starters license" at 17 as long as you drive under adult supervision).
And later on you realise that often taking the car, whilst great, isn't that more practical (and certainly not as economical) as taking the bike now and again.
Another reason is our infrastructure, it is pretty safe with all those bicycle lanes, so parents do not worry too much.
Also if you live in the city then for shorter distances (under ~3km) it is just the fastest way to get anywhere and no parking problems.
Add things like that the Netherlands does not have a hot and moist climate, so normally not sweaty. Pretty low crime rates especially in regards to violence. Car drivers being used to have lots of bicycles around.
There's just a lot of factors down here that make riding a bicycle more attractive as in most other countries that I have seen.