Uh... have you ever owned a car long enough to need new injectors, radiators, or exhaust systems?

I've owned three vehicles that surpassed 400,000 miles, with one approaching 600,000 now. I've replaced a radiator once, and it was because of a small boulder tossed by a semi. Belts are usually less than $60, and are only replaced after 120,000 or so. Your average driver won't have to worry about those but once every 5-10 years. I've never had to replace a injector system (and if your dealer tries to sell you a service to 'flush' or 'clean' the injectors, decline; most auto manufacturers recommend not doing anything but replacing, as the service of cleaning/flushing is more likely to cause damage than actually be beneficial).

Fuel pumps are going to be brand-dependent. Don't buy ford, because good lord they suck and the pumps do go out, but again, I've never had to replace a fuel pump (my three are toyota, honda, and volkswagen).

If you pay for a tuneup, you're either racing or are a fool. One of those use cases isn't relevant to a discussion about the average person owning a vehicle.