But DBD::SQLite is quite a big dependency to have, as it includes the complete SQLite database code. The PPM includes the binary libraries. Plus the fact that several modules depend on specific features of a particular database, which are not part of SQLite. However, I do agree that it is another alternative.
It's not a dependency unless you want to run the tests. It just skips them if you don't have SQLite installed. I think that's more reasonable than trying to do a test that doesn't really prove anything.