Perhaps not the right choice of word but I mean the term 'neocolonialism' here in the sense of introducing peoples to our ways of life: democracy, capitalism, human rights.
The long and short of it is that, you can only get with the web of conflicting interests, pure monetary dealings, etc so far. You don't make any lasting alliance with a peoples and a system fundamentally opposed to you. If you isolate away, they will continue falling into the trap of systems like China and Russia who are quite happy to take your place and have completely opposite ideals to you. Eventually you will be left more and more alone on the world stage with no true allies if you let them keep doing it, and one day you will be finished off by soft or hard means when those entities, who kept expanding their outreach, became powerful enough.
Tldr; Defensive fire. Its not that you want to engage in neocolonialism, but you will have to do so as long as your enemies engage in neocolonialism. The logic is no different than that behind maintaining a traditional military power really.