Yes, matching the bobbin and top thread is very important because those threads that poke through to the top are very distracting and ugly:< I have to disagree that laundering it will make them disappear. I've not had a machine yet that I can put a different color thread in the top and bottom and not get this occasionally. You can play with the tension and get it just perfect and then do a quick curve etc. and see the bobbin thread pulled up. Not attractive. So, yes, it's easier and less hassle to use the same bobbin and top thread at the same time.