I have used them for thread for a second needle, or threads for the serger (needles) instead of two spools, I have also used them by separating embroidery floss, pulling out a strand and winding on a bobbin for piece work either by hand or sewing machine and that thread was the perfect color and I don't need to run around looking for a spool. When I use the embroidery thread on the sewing machine (not the embroidery machine), haven't figured out how to "flag" the end yet so I can change before I run out.
Marysewfun