While I too think that market segmentation as it exists for digital goods is stupid, I don't think it is done just for the money.
Different countries have different laws, different taxes, and your home country has different treaties and export control regulations that all need to be accounted for when selling to other countries. In some cases there could be markets/services that abstract some of this away, but it is not a trivial problem.
If it was trivial to do, then the only segmentation you would see would only be differentiating on price (getting the most that someone in that region would pay for it), instead of not selling it in those countries at all.
Now, the RIAA/MPAA has deep enough pockets and plenty of lawyers that they could have figured all this out for themselves already, and could have built a great online distribution system for themselves. So for them, segmentation is purely a play for money, though (hopefully) it will hurt their profits in the long run.