Is that really a large subculture, or is that mostly car rental places cycling vehicles through their fleet?
The rental companies typically buy vehicles from the manufacturer at such a volume discount, that they're able to flip them onto the used market a few years later and come out even with taxes benefits factored in.
There are also private and corporate leases. In the UK at least 20-30% of new car sales are leases (it's a tax efficient way to get a new car, particularly EVs), and these usually run for about 3 years, after which they're sold off at trade auction.
The rental companies typically buy vehicles from the manufacturer at such a volume discount, that they're able to flip them onto the used market a few years later and come out even with taxes benefits factored in.