Many parts in a car, so many things that can fail

A modern car (after 1980) has a couple of thousand parts, let's assume 4'000 to 7'000, not counting ingredients in the electronics section. This is a lot of parts, and any of them can fail with the car becoming older and older. You think it might be a simple problem to solve when your car doesn't start easily when the engine is warm, while starting without problem when it's cold. Well, there are at least 20 to 50 parts that could be the reason of this and maybe you have to replace all of them to really find out which one it was. With modern cars this has become even more complex. So complex that the only thing mechanics can do is to plug in a testing unit, connect the result with the car manufacturer's computers and receive instruction what to replace next. Older cars are "simpler" and therefore the mechanic is king, not the computer. What you learn during these adventures is that many parts of a car have never been built to last 30 or more years, i.e. the fuel tank, the pipes between the fuel tank and the engine, cables, wires, etc. That's why keeping a car alive is an investment too, not just buying it.