I used to work with a guy (a few years ago) who had a Mk4 Astra and he would never service it apart from doing an oil change once a year. He had done this for years on different cars and would get some hefty mileage out of them (he was on a car allowance scheme at work and did a lot of motorway miles). Only when something went wrong would he fix it. When a car did go wrong and it was beyond repair he would simply buy a new one. I think the whole thing was done on a profit basis for him. Buy a car for £3-4k, don't service or look after it and get £400 a month car allowance. Makes a profit of over £1k a year from doing that (times that by a few years if the car lasts and he has made a tidy little profit).
In the time I have known him he has never had a belt snap but then again he is lucky. Not worth the risk in my opinion as I have seen the aftermath of a belt snapping - it's not pretty and costs a lot to repair!
A mate at work is exactly the same. He's got a 1996 vectra with 180,000 miles. He brought it 3 years ago for £400 with 130,000 miles on it. It that time all hes done is change the brake pads, tyres and topped up the oil if need be!!
Hes not on car allowance but it costs him bugger all, if I ever had a car and didn't service it like that I just know it would break!!
We also changed the cambelt (which has never been done) on my brothers S reg Starlet a few weeks ago and it was frayed quite badly but still hanging on in there.