Why look up records for only the last eight characters of a VIN? It's one way of identifying typos, for starters. But there's a more sinister reason that you might want to consider.
Let's pretend that a nice old green 1969 Plymouth Road Runner 383, VIN RM21H9A100001, was sold to some huckster. Eventually it made its way out of the U.S. to, oh I don't know, Montreal perhaps. All records of the car stop at this point and it quietly disappears. Some time later a freshly restored red 1969 Hemi Road Runner, VIN RM21J9A100001, shows up for sale in California. Wow, it sat in a barn in Alberta for 30 years (or so the story goes), was restored and sold in Vancouver. What a find. Too bad it doesn't have a documented history.
Records of that nice old 383 Road Runner still exist somewhere. If they are entered into this database, then looking up the last eight characters of the VIN, 9A100001 can prove worthwhile to potential buyers of that very expensive 'Hemi' Roadrunner. Not to mention the Feds.