I find the common problem with automatics is their service time scale. Bad car owners often forget to do oil changes often enough and those are only 3.5-10k miles apart depending on climate/oil type/etc. Which means services that happen every 50-75k miles or greater get left to people that actually maintain service histories and timely maintenance.
Personal example buying a used car with 60k miles that had some idle/start issues at times but generally ran well. Everything seemed to be serviced in a timely manner but the spark plugs were still the originals. Those spark plugs have a generous "100,000 mile" service interval. I pulled the originals and sure enough they weren't in the greatest shape. $40 later I never had start/idle issues again for the remaining time I owned the car.