F'real they're just better SUVs. I tried googling it, but the internet's very helpful answers were "they're not cool" and "SUVs are more popular." I'm convinced it's manufactured desire. What really happened to the minivan?
Edit: Apparently wagons and minivans still exist, they're just sold as SUVs.
I think they got associated with the "Soccer Mom" stereotype (Which was basically "Karen" before Karen was a thing) in the minds of the public and it stuck.