Boots are bulky, which is an issue when flying with a small carry-on backpack. It's amazing how much you can stuff into boots, then further reduce the bulk by tying the laces tightly.
I took the pictures at the top of this post a few years ago to show the contents of my boots. I no longer stuff anything metal or electrical into them since my collision with London Heathrow Security. I was grateful when the kind official put my suspicious-looking boots back through the X-ray scanner, rather than have me empty them.