Why your plane does that steep takeoff thing, and why there are no late-night flights.
The curfew was established as part of a settlement between the County of Orange and surrounding communities (notably Newport Beach) who were concerned about aircraft noise. It's been in place since the 1980s and is strictly enforced.
SNA is famous for its dramatic departure procedure. After takeoff from the short 5,700-foot runway, pilots apply full power and climb steeply. Then, around 800-1,000 feet, they dramatically reduce thrust — this is to minimize noise over the neighborhoods below. It feels like the engines cut out, and first-time flyers sometimes panic. It's completely normal and required by the airport's noise abatement procedures.