>>513848998 (OP)
Because we live in a fiat system which without infinite growth becomes a zero sum. Every dollar ever created will evaporate to pay debts and every asset will end up in the hands of bankers to cover debts.
In the event of population decline you enter a spiral where people don't take out debt which leads to established businesses not being able to sell enough product to continue producing, selling, and paying debts. Standing orders go unfulfilled and it ripples through supply chains.
For example an auto manufacturer can't sell their cars and in turn pay off their steel producer and as a result the steel producer goes out of business and then the businesses that rely on the steel producer in turn go out of business.
The alternative is to import a new populace untouched by debt and use government to put new debt in public trust because they're too stupid to do it themselves.
For example putting them up in migrant hotels and employing them below cost.
At the moment America is entirely driven by the MIC.
Until we start killing bankers and instantiate a new system we're up shit creek without a paddle.