Storytelling With Analytics

I recently had to do a workflow from SharePoint Designer 2010, that sends an email once a list item is created. After publishing it to its associated list in SharePoint 2010, I found that the workflow was not automatically starting when I create a list item, but when I manually start it, it would work. After some research, I found that I initially created it using the system account. So I then tried to use my own user account that was site collection admin on the site, to re-create the workflow, published it, and it now worked. Am still yet to understand why this is so.