Customers:  "We have this great way of attaching rear lights to our bikes.  Two small holes on a bracket fitted to every rear rack or the same two holes on a rear mudguard engage with a simple pin on the light into one hole and is secured by a effective bolt through the other hole into the light.  It never fails."
Marketers/Bike company:  "Let's change it."
"Attach it to the seatpost," bleats the salesman in the bike shop as he shows me the latest lux/lms/Lith Ion/USB death ray wonderlight.  "I'm on a traditional sized road bike with a horizontal tube with a small under seat bag.  No room I say."
I couldn't understand the added abuse I got from drivers whenever it rained and I had to ride at night.  Eventually the penny dropped.  My jacket covered the light rendering me unlit to following drivers.
I have mutilated and bodged lights since then just to spite those clever (?) marketing executives!
Sorry for the hijack OP, I have had a stressed morning that has included a critical Mother in Law and trying to find two small hedgehogs in the World's most cluttered garage!