In the world of database programming, why do programmers create database objects with statements like:

Dim mydb as database
set mydb = createdatabase("mydb.mdb", dbLangGeneral)

etc. etc., I think you see what I'm talking about.
The Beginner books that I own, never seem to go into the issue, and the other books I have, seem to skim over it.
Question: What is the advantage, Why not just let the DAO or ADO object do it all?