In Photography, What is the primary drawback of the light meter?

I have four light meters ranging from expensive to dirt cheap. The one that I like the most is a Gossen Pilot, the old one that comes in the little grey case. It is stupid, simple, easy to use, and uses no batteries. There are more recent Pilot models, but this one has been in my camera bag since the dark ages and it still works. And anyone who has a small screw driver and another light meter can adjust it in seconds if it goes out of calibration. You can probably find one for $20 to $35 easily.