I can see what you are saying about defensive playing. What is ultimately comes down to however is the objective of the battle. If you set an objective for the game that requires one group to cross the table, and give it a turn limit, then those soldiers will have to go eventually or simply fail.
When you think about it though, soldiers that aren't ordered to advance would really just sit in cover and hope to hell that they don't get killed. But when that Soviet Political officer orders them to advance, they have to get off their but and advance!
That being said of course, I have seen advances made with great success on occasion. But it is hard to advance in the face of an entrenched enemy! One thing that I found is that you should move your whole squad out at once (as you can either move them out one at a time or all at once). After moving them out all at once the enemy doesn't start taking in-sight tests until all of the squad (or group) has moved out, thus making it much more likely that some will not take fire or will not duck back and then hidden enemies will be spotted. After that let the slaughter begin

Also, move out those big machine guns (in the case of NUTS! and FNG anyway) along with the group and cover them with bodies until they can set up. If you even get one set up out of three then the enemy is in real trouble.
Anyway, hope that helps a bit...
n.