Repentance and Baptism Question

I realize this question could lead to controversy.  But I really am curious as to why this is.  I do not know the answer although I am trying to figure it out.  Here is the question and it is mostly for my Lordship salvation believing Southern Baptist brothers and sisters. 
Why do we make certain that we make repentance part of what you must do to be saved but say that baptism is not necessary for salvation?  I ask this because of Acts 2:38.  Those hearing Peter’s sermon were cut to the heart and asked what they must do (which is probably asking what do we do to call on the name of the Lord as Joel prophesied).  Here is Peter’s response:
“Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit.” 
Why then do we (Southern Baptists) tell people that they must repent and believe but we do not say they must be baptized? 
Thoughts?