They are not very flexible, not really durable, have more friction and are also thicker than normal cables most of the time. So it's really obvious why they suck.
One company starts to use them and states something like "braided cable for more flexibility and durability" and everybody believes that crap and almost every other company jumps on that bandwagon, so it's a given that every gaming mouse *needs* a braided cable. As Skylit said people really list non-braded cables as a big con nowadays and I don't know if I should start laughing or crying if I come across one of these reviews. It would help a lot if people would listen less to the marketing machinery and make more use of their brains and intuition.