When you set the controls on a compressor, you are setting a baseline. The unit will try to bring all sounds into that baseline by boosting the weak signals (like a harmonic) and dropping the loud ones so the volume level is more consistent.
The term `compressor`is slightly misleading, since it`s also a booster of sorts.
You lose a lot of dynamics. Depending on what you play, the ability to create drama and tension by making the music softer and louder is a big part of the delivery.
That`s my take on it.
...so ever since then, I always hang on to the buckle.