I don't have straight stitch plates for either of my machines so I use leaders a lot, always when chain piecing. Holding the thread is so ingrained in my brain, that 'nesting' has never been a problem, but 'fabric stuffing' can be without the leaders. I never use enders for several reasons.
Using leaders does not save any thread for me (it actually uses more because it's more sewing), but it makes for even starts because of the sole plate issue and that's worth it for me.
I use the same small folded over pieces over and over and have been known to trim and use them as embellishments on art quilts when they are finally retired from active duty. :oops: