BMPs are large but fast: The software does not need to process the image before displaying it to the screen, it simply "dumps" the bytes directly to the screen. For this reason, BMPs are usually used for operating system specific imaging (e.g. drawing images in a window, icons, wallpaper etc.) where display speed is very important, but are almost never used on the web where image size is premium.
The term "device independent" means that the bitmap specifies pixel color in a form independent of the method used by a display to represent color.
As i said before BMPs are raley used on the web because of their size and the pic below demonstrates this. The file size is 89kb.