BeerHouse MVC Kit-Unnecessarly repeating data in Post Table

Question

I was going through the BeerHouse MVC project.
In the forums section, the Post table in the database looks like repeating the same values. I can see the colums like -AddedBy, AddedDate, LastPostBy, LastPostDate. If we want to get the LastPostDate and LastPostBy from the table why can't we search the latest AddedDate field of each post and find out the LastPostDate and LastPostBy? Why should we use additional fields in the table for the same purpose? You can do the same for ReplyCount and VoteCount.
Thanks,