Just a thought here. Older cars would probably not run right if not kept tuned up. They would chug-chug along and annoy the driver so badly that they would eventually buy a set of spark plugs. As for newer cars, I think they only get tune-ups at the 100,000 mile mark. I might be wrong.
Sadie
My experience has been mostly with motorcycle engines, but I had a bike with modern hydraulic tappets (a 1984 Honda) that did not require adjusting. My current bike, an older model (1981), requires a valve adjustment/check every 3,000 miles on top of the standard fluid/filter change. I know, specifically, that a 1959 Chevrolet V8 requires a valve adjustment every 3,000 miles. I'm going to go out on a limb here, but unless your car is more than 25 years old, you probably don't need a "tune up".