You can easily wind your own thread on a spool easy with this method.
Take a bobbin and glue in on an empty spool, now you can put on your machine and wind your thread on it.
Why would you want to,
No need to buy several cones of serger thread for a project, just make a few of these and use them on your cone older, most cone holders can accommodate a regular spool of thread.
Or going to do some topstitching and need another spool of the color thread.
I am sure you can find many uses for the method of winding you own spool of thread.