Why is my recovered file smaller than the original?

This could be due to many reasons.   The most common cause is what we call 'bloating'.

In Access databases, when you delete objects such as records and tables (or in fact any object), Access doesn't really delete them, it just flags them as 'deleted'. This means that when you delete objects, the filesize does not reduce.  The only time they are really deleted is when you run the Compact option (or Compact and Repair) from Access.

When we reconstruct your file, we don't recover the 'bloat' therefore your database is effectively returned 'compacted' (in terms of Access).

Obviously the alternative is that some data/objects may not have been repairable and therefore lost.  If this is the case, you should be able to tell by looking at the recovery report details - particularly in the Unrecoverable section.