If we see someone in a uniform, fluorescent jacket etc often we will naively not request to see ID etc.
Scammers know this and will play on it, this scam effectively gets people to part with cash or cheques for parcels they didn’t order.
It is extremely simple and even the most intelligent people are victims to this crime.
Think about who any parcels are from, if you don’t recognise the company sending you the parcel then Google them quickly, we would probably never pay for anything on the doorstep like this, if they’re a legitimate delivery company they won’t mind you turning them away and coming back the next day. Either way, be careful, ask for ID & then ring the company/Google them before paying for anything. Ideally open the parcel first!