A single blade chucked in the recycling may get stuck in something else or in someone's finger or simply end up in landfill because it is too difficult to sort it from the bulk of the waste. A pile of blades packed inside a suitable container that holds everything together will get picked out, probably automatically by a magnet, and recycled along with the rest of the ferrous metals.
On a similar topic, it was bugging me that our local recycling system didn't cater for aluminium foil, so I made a few phone calls and eventually established that although I could not put foil in the recycling bin (we have one wheelie bin for rubbish and one for recycling) I could collect it over a period of time and put it into a can bank. So we now save all our milk bottle tops, foil wrappers and roasting foil, and when I have several can-sized balls of foil I put them into can bank the next time I pass one. Dead simple and requires little effort. (The reason it bugged me was that recycled aluminium uses 5% of the energy needed to make the stuff from scratch.)
With only a little thought, recycling is dead easy.