They aren't targeting customers like you. Neither am I. You have a 15 year old car that you maintain yourself and a lifestyle that is willing to be interrupted by failures. "Don't fix it unless it breaks" is one philosophy - one that is *sometimes* successful in saving a tiny little bit of money. But over here in the real world where people rely on their cars to arrive at their place of work where they get paid far in excess (amortized) of the savings from attempting their own repairs, missing work, and paying tow bills, etc.... it doesn't pencil out to be profitable.
Not to mention - no military, aviation, government, or other important organization has ever concluded that preventative maintenance is a bad idea long term. And generally speaking we are a specialized society. I fix cars. Someone else bakes my bread, and some other guy cobbles my shoes. Just how it's done friend.
If you do it for funsies that's fine - but don't be mistaken that you are saving money. You are trading time - and time is often more valuable, and is directly proportional to money at some rate.
We do a lot of preventative maintenance and we pride ourselves on keeping our customers fleets at a full state of readiness at all times.
GD