Similar to Perl, SQLite doesn't do strong typing. They seem rather militant about it, in fact.
This behavior is a feature, not a bug. A database is suppose [sic] to store and retrieve data and it should not matter to the database what format that data is in. The strong typing system found in most other SQL engines and codified in the SQL language spec is a misfeature - it is an example of the implementation showing through into the interface.