china is neighbor to most of the former soviet republics in central asia whereas pakistan isn't. to construct a pipeline that goes through pakistan sounds like enormous economic waste. and today chinese government resents the idea of dictating economically unviable policies to its big businesses. unless pakistan's economic situation is absolutely bleak and thus poses an imminent threat to its national security, china won't do such a thing to subsidize pakistan's own consumption and transportation of energy - and pakistan shouldn't welcome a scenario in which china had to massively transfer wealth or subsidize pakistan's economic needs because it would have signaled a country on the very brink of collapse
not to mention china sees the chaos and suffering in pakistan a result of american meddling in both afghanistan and pakistan and pakistan's ambivalence towards anglo-americans' evil design. therefore, any economic subsidy to pakistan at this point goes on to subsidize american war of terror. so china's priority is to encourage pakistan tp take stock of the whole situation with US and pakistan's actual neighbors (who actually have high stakes in the future of afghanistan) and not to financially underwrite the indefinite prolonging of this strategic equivocation on the part of pakistan.