Why? (about Atlanta's punt formation)

Why didn't the ST go for the block when Atlanta was punting out of the endzone and did their bull excrement "spread" formation? Atlanta's ST kept sending all their guys down to cover the punt and were only leaving three or four guys to block. It would've been incredibly easy to send a guy off the corner and get to the punter. The game was still on the line at that point and it would've killed the momentum Atlanta's D had......