Why Do We Drive Our Flying Cars in Lanes?

Traffic Lights? We don't need no stinking traffic lights!

Everyone does this! Furturama, the Star Wars prequels, even Back to the Future!

If your Sci-Fi has flying cars, chances are they will all fly in lanes just like their modern day counterparts, despite the fact that they can, you know, fly!

I can understand having roads and lanes when you can only travel in 2 dimensions and there are big things like buildings around but every time I see “Gridlock in Space” I start shouting “Just go around!”

Is this just me? Am I missing something?