It has been estimated that when the German army moved on Stalingrad, accompanying them were about a half a million Soviet volunteers. This number is questionable, but it is true that there was an organized effort to aid the Germans. As late as the end of 1942, the Russian National Committee was formed which issued the anti-Stalin Smolensk Manifesto, which urged all Red Army personnel to desert and to fight with the Germans. If the population was this determined to aid the Germans, the Germans must have been even more determined to convince them not to. Many of the people who had volunteered to help the Germans were Red Army soldiers who had surrendered.
Every soldier shoots any Russian soldier found behind the front line.
This no doubt provided a disincentive for surrender. Moreover, the behavior of the Germans boosted the morale of the Red Army and gave the Soviet propaganda machine something it could use. Many Russian POWs were starved to death as part of an attempt at extermination. One source puts it at 3.3 million. Another puts the death rate as high as 4.7 million.