Devising molds for straight-sided carbon rims is evidently a piece of cake compared to doing the same for rims with hooks. Remember, straight-sided rims meant for use with high-pressure tires had vanished from the market by around the mid-'80's. But when carbon rims became fashionable for high-performance road bikes, suddenly manufacturers were claiming that straight-sided rims were best ("Save 50 grams per pair of wheels!" or whatever it was).

A spokesman for DT, interviewed on the topic, said that they'd investigated the alternatives and chose chose to manufacture all their carbon rims with hooks. Paraphrasing: "We don't mind investing in the technology to build a safer and more reliable rim." Sick burn against the other rim manufacturers.