I think this misses another equally important reason, which is to do your part to help build the gift economy upon which we all rely in our day to day work. Near every common solution and recipe has been written up by someone, somewhere, and we all make use of these gifts.

When you learn to do something useful that other people will likely also have to accomplish at some point in time, write it up. Not only will it benefit people out there in the world, but it is also a great way to ensure that you yourself don't have to reinvent the wheel a few years down the line. Who remembers the details after that long? So write it down, and if you write it down, you may as well publish it.