Due to the nature of footprints, they tend to wear out faster than other components.  It is cost-effective to manufacture footprints at the same time we produce the tents.  In our quest to constantly improve our tents, dimensions and attachment methods change from one model to another, and sometimes from one year to another.  A footprint from a similar looking tent or newer tent probably will not fit a tent that is a couple of years older.  There are many do-it-yourself options available online.