I doubt people are doing it to avoid paying for servicing etc, that doesn't make sense to me. It will be because of lease/finance agreements, or re-sale value on owned cars.
Cheapskates are gonna cheapskate though - I very much doubt the market of people looking for ways to get cheap 5,000 mile per annum PCP/lease deals fraudulently when they're really doing 25,000 miles, is full of service conscious people going out of their way to make sure the oil changes are still done on time.
They'll dump it back with the lease company and move on, not a care in the world.