There were night attacks in WWI, just not on a major scale. Attacking at night was a difficult venture, be it WWI, WWII or the Second Anglo-Boer War. That said, trench raids were often launched at night to collect intelligence and harass the enemy. The attack on Bazentin Ridge, on July 14th, was preceded by the British divisions involved moving up to their jumping off points during the night, while just recently was the 100th anniversary of the fall of Bitlis to the Russian Army, which captured that Turkish fortress in Armenia via a night attack.

Given the manifold communications problems that could ensue, the need for accurate air and artillery support, and the training requirements that full on offensives at night would have demanded, they simply weren't worth it.