Intersections are a necessary evil when it comes to building roads. You need them to keep cars from crashing into each other, but at any given time a large number of people are just sitting around waiting.
To be fair, engineers use traffic flow analysis and other methods to try cutting down the wait times, but it's often still a one-size-fits all approach.
That's why you can be sitting at a light when there's no traffic going the other way. Or you might be in a huge line of cars, but the light only goes green long enough to let a few through (this is a problem at an intersection just outside my office).
In Europe, they solve this problem with roundabouts or turning circles, but those haven't really caught on in the U.S., at least for major roads. So, is there a better solution?