I have seen and heard this question asked many times, “Why bother? When most everyone viewing my images isn’t using a color calibrated monitor anyway?”
Here is a thought, if you don’t calibrate your monitor, you have no way of knowing how far off the colors are. If your monitors colors are off by quite a bit, picture someone else viewing your image with an uncalibrated monitor which is off also. The colors wont even be close to what you think they should be.
If you have a color calibrated monitor, at least there is a greater chance that what the viewer sees is close to the intended colors.