If I had to guess? Just tradition, probably. Actually they don't all have silks on both ends. La Bella's flats don't. Neither do GHS's flats. As for Dunlops, SITs, and the others I can't recall - and haven't tried yet? Couldn't say one way or the other... Most European flats do have both ends wrapped; the Rotosounds, TIs, Optimas, Dogals, Gallis, Pyramids, and factory Hofners I use do, anyway. And so do the Fender 9050s, DR Legends, Ernie Ball Cobalt Slinky Flats, and D'Addario Chromes I'm using - or have used. The 1st generation Sadowsky Blue Label Flats on my Carvin LB-20 have silk on both ends; I imagine the current Gen 3's still do, too. Ball end silks can be a PITA on some basses; the ball end silks of the Dogals, the Optima Chromes, and the Sadowsky Blue Labels do actually come up on the E string saddles of the basses they're on. But they stop just short of the string slot, so...no harm done. Which, I imagine, is why La Bella and GHS only have silk on the tuner end...

And, no; it wasn't a stupid question...
