Many databases benefit significantly from being able to optimize knowing that a column is a fixed-width integer, for instance (or a timestamptz--especially when it comes to sorting and indexing!). SQLite has not historically cared much about these kinds of optimizations because it does not compete particularly well on execution speed with other databases for anything but very simple queries.
if stronger type systems will ensure performance, Haskell will beat C in benchmarks but that's not the case in most situations.