There are only two reasons: (maybe more but two is plenty)
1. If you want to promote here, you need to be logged in. While your identity will remain private, we generally will not publish any submission that does not have a validated email account on record. (Visitors can write a comment however it will not be published until it's passed a moderator review.)
2. You are an author/regular contributor
There are three different roles you can play here. Author, Moderator or Comment-er. If you plan to contribute on a regular basis, having an account here is a good idea. Having one will give you more authority and makes less work for us. e.g., When you comment with an account, we will "approve you" after your first comment so all your subsequent comments will be published immediately.
Important: Creating an account does not put you on our daily dlmReport. If you want that, then you should add yourself HERE.