The Barnes & Noble Bookstore (at least the two or three I have been to in the past 10 years) has a single queue. Fry's Electronics did it that way. The self-pay corral at HEB (a huge Texas grocery chain) with about 14 check-out stations does it that way. The Academy Sporting Goods store near me does it that way. The Austin Bergstrom Airport security gates are that way.

I agree that many places have a queue for each registers, but the other way isn't entirely rare.