Who doesn’t need to keep track of all the planning which goes into a trip? Pieces of paper, bookmarks on your browser, memory: all of these are fallible. On the other hand, blogs never forget (if you remember to post). More, very helpful people may leave little tidbits of advise for you.
Then, when you are back, you need to share the photos and the memories. What better place than the blog which got you started.
So that is why you see yet another travel blog. Think of it as a friendly pub in a new city where you can come and chat about your trip for a while.