It's a pretty standard policy from a sales standpoint. Properly localized products typically sell better on the whole, while mish-mashed ones can be a huge issue depending on what the item you're trying to sell is. An English track being a requirement is basically trying to make sure everything sells as much as possible, barring a few examples here or there.
Is kind of frustrating though from the perspective of "I'd really rather just get the damn game", given in some cases they'll just walk out if they can't get it released without a dub as they ARE expensive as noted, plus some are set to only have a niche appeal anyway. At least DD offers something of an out, but I still think it's kind of shitty, especially as some of these games come from publishers who are more inclined to make a decent retail package.
Yeah, from what I've seen, most of the games seriously affected by this are rather niche. Games with broader appeal would be more likely to have localized audio regardless, since the publisher would surely see it as financially viable. So having it as a mandate does more harm than good in the end, at least in my opinion.