If I was to put a popsocket on my L2, I'd not be able to put it down flat and I'd never get it in my bag for taking my L2 with me when I go out.
To answer this, I'd say, look : there's another side! Yes, you can put down your Kobo on the screen side on a flat table. Wow.
Also, you can push the popsocket down. It will fit in a bag.
EDIT : Some people buy a clear case and stick the popsocket on it, with colourful stickers to personalize their ereader.