While I first thought that a "good" design should be able to sell better I changed my opinion. First, those LP are tested. Come on, it's not that those people aren't making money and can't afford designers to come up with some fancy shit. Even the hot sellers, with products/services that cost several thousand (ever seen stuff from stompernet etc, where you have to spent a few thousand $ ?) use those ugly LP! Many of those hotselling LP spend a lot of money for experts, they hire the best copywriter they can get for their cash to build them one of those ugly LP!!
While my own designers heart cries out loud my brain tells me to go with those LP, and I will do so, because I want to make money, and that's obviously the way to do it.
As to why you don't see those LP in other languages like german etc? Well, I can answer for Germans only, I believe that both the marketer and the customer there are kind of arrogant. The marketer want to be "better" then his US counterpart and provide a pretty solution (page), and the customer thinks he deserves the extra amount of work that is put in a fancy page when he/she shops around. But I'm sure that they will also fall for the "ugly" LP, prove of it for me are offline stores like ALDI - while premium stores are nice and everybody wants to be seen in them ALD sells a lot more and the owners are immensly rich. ALDI looks ugly and cheap (while in fact the interior is pretty expensive!), so everybody thinks that the products there are cheap, and they go and buy! That's the trick, and I think it's the same with those LP, if they look fancy and perfectly designed nobody believes they get a good price there, everything is perceived as being expensive.