i use them for sewing, piecing, quilting, hemming, mending....if i am sitting at the machine i am using a schmetz needle; lots of times quilting or topstitich or sharps. the needle and thread have to 'match'; the purpose...?; i don't know if that really matters. the thread/needle combination are important because the incorrect size needle with fray or break you threads. there are certainly people who always change to the (correct needle) for what ever they are doing, universal for sewing, top stitch for top stitching ect...i am not that.........
worried about it, i use needles that work best with my threads. and i don't stress over whether or not it is what the 'purists' do. i've been sewing for 45 years and when i started sewing we did not have so many choices you learned to make do with what you have.