The air flow meter is unreliable and as they age, their readings change and change the tune as a result.
They are also slower to react to what the engine is doing as they measure the intake system filling up as well as what the engine is doing, making the throttle slower to react to your foot, as well as basic stuff like when they do die they are $300 each rather then 70 for a map
Oh and there's always they poor person stuck on the side of the road who blew and intercooler hose, cause a map doesn't care and will still be drivable