Because that seems to happen every year, oh wait...we get Dexter Jackson and a 400lb Sam Adams who was worth having 4 years ago.
Smith had 82 tackles as a DE and 7.5 sacks. More tackles than Adalius Thomas, more sacks than Jared Allen and same amount as Alex Brown.
I do not believe anyone would argue that Smith is worth 8.6 million, but the Bengals need to keep him. He is a very solid NFL DE.