They don't by default, because they didn't in older versions of
SQLite and some older applications might rely on that. You have to
send an explicit pragma prior to opening a transaction to make them
take effect.
We'll keep the door open for side-by-side support of Postgres in
the background, but due to SQLite's type system quirks we cannot
use the same DDL for both databases, so we would have to maintain
two sets of DDL (schema init and schema migration scripts) at once.
Interested future contributors can shoulder this maintenance burden
if they so choose.
