If you can't get work done after ten years, you've got an expensive paperweight. I just found out Vespa won't work on scooters older than 10 years, in my area. That's hurting them in the long run. The scooter scene will be harmed if you can't rely on getting your money's worth from a scooter.
I think this came up here somewhere else...and i feel ya!! I became aware of shops unwillingness to work on later models to be a thing when i got my first bike decades ago. So its not just scooters by any means.
Even if a dealer would work on an old bike, the labor rate takes that option out of the equation for most of them. Maybe not the higher end bikes, of course, but for the most part, its cheaper to buy a new old bike than it is to have any type of major repair done at a dealer.
I had a shop close to me quote me $240 to change the back tire on an old Benzhau scooter (Roketa/JCL/Johnway MC-250)
Just not feasible for a $700 bike