Why do airlines lose bags?

Seriously. The state of the art (FedEx, UPS, DHL, etc) is to pretty much never lose anything. FedEx's ability to get something I drop off at 9p in Ohio to the west coast the next morning is nearly magical. Moreover, they have an amazing logistical system that knows precisely where every package is at all times and they make this real-time data available via the web.

The airlines, however, seem to consistently delay or lose about 1% of folks bags. Worse, if you've ever lost a bag, you know that it takes them about 12 hours to even figure out where it is! And you hear lame excuse after lame excuse from the airlines about aircraft weight and balance, cargo capacity, weather, etc.

Last time I checked, FedEx flies the same airplanes and is subject to the same weather and weight issues - and yet they find a way to get things where they need to be.

Airlines: please, please, please: hire someone from FedEx and solve the problem! We know how to do this, why make us frequent travelers continue to suffer with delayed and lost bags?