You drop it into your pocket, whatever it may be-- the phone, the keys, a penny you found on the sidewalk sunny-side up. And there it is safe and sound, there it'll stay. Just a slight reach away. The security of carrying something on your own person, of keeping it in your possession, under your protection. Almost like a friend.
Whoever invented pockets needs to down in history with the inventor of sofas, and sunny saturday mornings, and singing in the kitchen.