For as long as I can remember, 'Well fans have complained about certain players "not tackling" etc. From Brian McLair to Gary McAllister. I even heard it leveled at Bobby Russell and Davie Cooper.
If Ainsworth continually tracking back means he's not going to be available for the out ball, or that he can't make as many forward runs, or that he tires quicker, then I'd rather he didn't do it. His net contribution to the team has been positive and hopefully he will be around next season to build on that.