> everyone involved in allocating and spending the money you give to build and supply that natural gas pipe is also selfish and short-sighted, and is much more likely to try to enrich themselves over providing a good service.

The point where the money is allocated to one goal or another is when someone donates the money altruistically. They are hopefully trying to be less selfish and short-sighted.

Sure, the implementors will take some profit, but so will any business to which the recipient could give the money.