Stalin viewed Vietnam is the strategic location of the Indochina, essential yet sensible to the political changes. Along with China, it will be the step to spread the Communism to the rest of the Asia.
Second, we're recently planning about planned economy. But, for the time of total returning is not yet. Since we're just escaped from war merely about two decades (after the messes with China partially solved), and those had forced us starting again from the scratch. We need more time to solve many problems still lying on the road toward Socialism.