billym is right that spoons work best when trolled or retrieved. In the SAS Survival Handbook it's recommended that you let spoons sink as deep as possible then 'reel' them in by hand.

Fish are attracted by shiny objects and movement which is I'm sure why spoons are included in even the most basic of kits.

The nice thing about flies is that if you have a fly which floats you can technically leave your line out (or many lines) and wait for a fish to think it's getting an easy meal. Unfortunately it's a low percentage method (I liken it to setting snares) because it's the fly landing on the water which gets the attention of the fish most times...not their presence just sitting on the surface of the water. That's why fly casting is such an art and a vital part of fly fishing.