This is because the same raw materials would have to be extracted at multiple places, more people would have to work at similar factories, producing similar goods.

Effectively, the world will be making the same 7 billion shoes except that shoe manufacturing infrastructure+supply chains+transportations will have to be made everywhere, thus expediting environmental degradation.

A lot of extra work will be done to find the same efficiencies everywhere.

Shipping for 7 billion people is actually very efficient.