I have confirmed that there at least exists one reason to keep blogging: You can keep your account active.
I registered with Blogger in 2005. I'm not sure how many posts I made (not many, for sure), but I did save my login info. When I tried to log into Blogger, my blog name had been acquired by someone else. I'm not sure how that can happen, but it did.
Be warned. If you cease blogging, you will be forgotten...
