Have the same issue here. 2 of 3 daughters daughters still at home, one 18 and the other 20. If they are secondary drivers on our policy they are only about $50/month to carry. Add one more vehicle and things get offside. We are either to be destined to drive them around, give up our own vehicle or public transit - uber, et al.
The insurance companies have been allowed to get away with this for far too long. The impact on families and the young simply isn't right. I'm not that dad that will pay $10k/year so my kids can drive their own car just to chauffeur their friends around. F that. I gave them both the wonderful gift of responsibility. You want your own car, get a job and save your money for the car nut and insurance because this crotchity bastard isn't giving the insurance companies any more.