[tomkarlo]

Stores are moving towards this, but very slowly. The retail industry doesn't tend to innovate quickly. Generally, you see the more innovative / aggressive stores doing this now (Whole foods, some drug chains, Apple stores, Best Buy) but it could take a decade or more to spread widely, in particular because in many stores it requires a significant layout change to accomodate one long line - generally you need additional space between the front of the line and the registers so that customers can go to the open checkout, and some stores don't have that much space.