The problem is, for the most part, this reputation is undeserved. Yes, a lot of documentation is bad. Useless, annoying and boring. Admittedly, sometimes it is the writer's fault, but most of the time, it's because of corporate culture. In the high-tech world, the gizmo is god, the software is king.
Documentation is the old-tech, ugly little sister.
It doesn't break new ground. It's not what the people pay for. It's a necessary evil that has to be included in the package because the competition puts one in the package. Therefore, manuals are generally cranked out as quickly and cheaply as possible. Tech writers are brought onto projects at the very last second, given very little support, and very little time to produce a manual.