Not to go off topic, but what is the point to double open end, or double box end wrenches?
It seems to me that having two sets of combination wrenches would do every you could wan't?
DOE or DBE wrenches are kind of older ideas, and most people prefer combos, but the DOE and DBE have some advantages:
1) it takes half as many wrenches to have the same number of sizes
2) if you have one set of each DOE and DBE, you have two wrenches to use of the same size (you can put one one both ends of the fastener)
3) open ends are weaker, so making a shorter pattern wrench can be sensible for these to prevent overtorquing. Also makes the wrench less cumbersome. DOE are particularly good for plumbing, IMO.
4) if you need another set of a different length or style (long / short / different offset angle / flare / etc) you need to buy fewer wrenches, saving space.
Most of that doesn't really matter in a well equipped shop setting with unlimited storage, but can be nice if you've got to carry a limited number of tools around, or have a specific job that only needs open ends (or for that matter doesn't need open ends, and you can get away with just box ends).