Why do companies change their logo/wordmark (e.g. StackOverflow)?
StackOverflow had a nice logo.
To me, their new logo seems worse. (To me, it's an uglier version of the original logo).
Why do companies change their logo? New management has to assert themselves. This is the easiest way to get visibility. Have seen it a couple of times. Whether it helps the company or not, I'll let the marketing folks answer.