The Royal Mail delivers tons of ‘junk’ mail every week, often these items are unaddressed and are flyers/leaflets for businesses/services etc.
For most people they just go straight in the recycling bin so are a complete waste of time, money and resources!
Just to be clear, opting out means no one at the address will receive unaddressed mail items. If the post says “The Occupier” etc then it will still be delivered.
If everyone did it, prices for stamps etc would increase.