Metal Cans, Outdated?

I've never thought about it much, but on core77.com they bring up a good point. Why do we still package paint in metal cans? They're so difficult to close and open again when you need to continue painting or do touchups. The EcoPrazi lid is not only an easy way to store your paint, but it also stores the paintbrush that you used, so you don't need to wash it and waste all the paint still left on it.