Why isn't there a "check engine" light in airplanes?
With a few exceptions (modern aircraft engines with FADEC systems) a "Check Engine" light on an aircraft would be essentially useless.

In a modern car we have an Engine Control Unit which manages things like mixture and engine timing. The "Check Engine" lamp illuminates when the ECU has detected a fault that requires some sort of attention, but it's not usually specific as to what the fault is or how urgent the problem is.

In most light GA aircraft (like the Cessna or Cirrus in your question) the engines are straight out of the 1950s/1960s: There are no computers managing the engine for you, and the pilot is acting as the ECU.
The pilot should be checking the engine's health regularly (by looking at the engine gauges) and adjusting power, mixture, and propeller pitch as required.

Since there is no computer supervising the operation of the engine in most light GA aircraft there's no system to determine when the light should be on, so there is no "Check Engine" light.



Note that some light aircraft do incorporate warning lights for system status information. For example, the status cluster on newer Piper Warriors:

Top row: Low bus voltage, Pitot Heat off/inop, starter engaged.
Middle row: Vacuum inop, Alternator inop, Oil Pressure.
Bottom row: Not used on this aircraft.

The information provided by these lights is more specific than simply "Check Engine" - directing the pilot's attention to a specific system or condition. The lights are also not a substitute for regularly scanning the engine instruments and managing the powerplant, they're merely a supplement to catch your attention between scans.