Package Delivery in Local Loop

Why not have a single company for delivery of packages, for all package delivery companies e.g. FedEx, UPS and DHL.
Cut the number of vehicles on the road. Save the cost for each company.

Would this boil down to single monopoly?

Not really. The courier companies (FEDEX etc) would find another ways to differentiate themselves. The package would still say FEDEX or UPS. They would simply deliver the package to this local delivery company, who would do the rounds of the local area to deliver to the end user. Does the end user really care who put the package on his door? One other draw back is that the issue of responsibility shifts from one company to two?