Displays and advertising... all about being noticed in a crowded shop.
Whether they held the product or just made you aware of it most of these had a hard life and was thrown away by the shop keepers.
Good condition ones usually comes to market when someone discover "new old stock" that's been overlooked and ignored for years.
Mid -90's saw some early electronic displays with programmable scrolling text.
These are rare and goes for extreme prices considering what it is.