It wasn't a symmetric situation though. The Germans generally held better ground because they were the ones who initially made the decision to entrench after First Marne. They chose the best defensive positions they could find, and the French and British had to make do (although I guess there would have been exceptions, such as the Verdun sector). Politically, the French and British couldn't just sit there and do nothing or sue for peace because they had a vast enemy army encamped on their territory -- what terms do you think the Germans would have imposed when they were clearly at the advantage? Under these circumstances they had to launch offensives, and given that they were at war and in stalemate, this was not a mad decision although it seems like it to us a hundred years on. The real madness was in letting the war happen in the first place, and the real tragedy was the criminally slow pace at which the general staff on both sides learned the errors of their pre-war doctrines.