Automatic/manual valve body

I figured that was the case (can manually shift an automatic valve body) but I guess my confusion is why folks swap to a manual valve body. I assumed there must be some issue w/ shifting an automatic body if people want to switch to a manual. What's wrong w/ it?

I have an automatic valve body that will not shift out of 1st. I'm going to remove it and see if I can figure out why it won't shift but I'm really not sure what I'm looking for. I figured this would be a good time to make an upgrade if there's something better to have (w/o going full manual).