I often here about why they're toted to as having the barrels aligned to be hitting the same hole at a set amount of distance, such as 50 metres. Why?
To me, it'd make more sense to just have them parallel. It'd be easier to manufacture (I think) that way, and about 3/4" of an inch won't make that much of a difference (especially on big game). I mean, if you think about it, a deer's vitals are about 6 MOA (so being 3/4" of isn't a big deal), and I'd assume African big game is a significant amount larger.

And on shotguns, I've always heard you have to aim an inch to the side when shooting clays with a SxS, but not with a pump, semi, or O/U. Considering you're shooting many little pellets, possible making a shot pattern a couple feet wide, I don't think it matters much, no?

Parallell barrels in double guns would make sense to me as well. My guess would be some technical issue that makes this hard to do.

Just a guess on my part, but they are regulated to where they shoot, i.e. just because the bores are parallel, doesn't automatically mean they'll place projectiles next to each other in a nice pattern.

You'd need a sight on each barrel to aim the thing. With the barrels regulated, only one sight is needed.

As to 50 yds? For dangerous game at close range? Only thing I can think of.