A calibrated monitor gives you a known standard that images can be viewed by. Move to another system and this should not change too much. As far as printing I use manufacturers canned profiles and they are pretty darn good. Printers do not seem to drift during their life terribly (monitors used to drift a lot but LCD don't as much and calibration also takes care of that drift). The print may not be exactly what you see (and likely never can since one medium is reflective the other transmitting) but you get to know your system and can learn how things are going to change in the print.
The other thing I have noticed is people have vast different colour perception and no one really sees colour in an accurate way. I am colour blind and it is frustrating for me not to be able to go to someone whom I know has great colour sight and have them tell me what is off in a print when I can tell something if off but cannot identify it due to my colour blindness (or so I thought). So if things come out of the printer and I am happy I do not obsess that it is not exactly like the monitor and usually the print is better as prints just are better to me anyway.
The next thing if you got all that to match up then someone goes and displays the print under different lighting conditions the print will look different again. So what to do about that?
Now if you are reproducing something like a dress's colour for a manufacturer the whole problem is magnified and I do wonder how they manage to do that while keeping sane.
As far as calibrating a monitor goes I have found it is very useful. When I finally did this I found editing far easier as I saw when things were not right. This does not always help me know what exactly is wrong but sure is a good start.