Cause the manual is already paired with the 2.3 and it would cost a lot of time and money to engineer, build, produce, etc. Something that has potential to have a very small take rate (being that it is manual).
It would be nice though
I believe you can add "the tow package" afterwards. The guys at TFL seemed to be able to add a hitch and wiring to their first edition. Unless there is some secret thing to the package that I don't know about.