@Kaiolino:
Endings cost money.
Yeah but all anime have them (with maybe a few other exceptions), including cheap as shit anime that's on at around 2:00AM like Umineko. One Piece has a pretty big budget for each episode and is massively popular in Japan. I really don't see it being a money-related problem, though it may be money-related in some other way. For example, maybe it's been shown the OPs do better in the singles charts than EDs. If they make a huge OP and put all the OP/ED money into just OPs, they get a better pay-off from the chart sales?
Or maybe some thing else like they want to keep people watching for whatever's on right afterwards so they dropped the ED as they found people tending to turn off or turn over during the ED?
Whatever the reason is, it's odd how only One Piece seems affected by it out of all anime series (though, again, apart from the inevitable handful of other cases).