I don't understand clan wars, they're stupid >>
When I first started playing I thought the same thing, now after more than a year of playing I still think they are pointless. However, from the standpoint of a clan leader/founder a war can be helpful. When a clan is losing members and interest in clan hall is lagging, there is no better of a lightning rod to create interest than a war. It creates an interest and buzz in clan halls, and brings a sense of unity to a clan that was bored out of its mind with people eating cookies all the time.
Although wars are pointless in the end, they are measuring sticks to clans and clan leaders. Finding out who is seriously loyal to a clan is easy during a war when both sides have members that everyone has a chance to kill. Having an genin that could kill other members of your opposition easily, but never doing it would raise red flags about their loyalty.
Where as other members gladly come into clan hall happy, giddy, and discussing who and how many people they killed. In a nutshell a war brings out teamwork and the natural instincts of preservation and most importantly survival.