If we do not know whether you are going to Santa Monica, Pasadena, Irvine or a cruise in San Pedro, we will default to LAX and say so. Send the neighbourhood in the first reply and the airport can change.
LAX
Tom Bradley (TBIT) still takes a large share of long-haul. Domestic terminals are a different walk and a different TSA story. A published connection that looks legal can be ugly if you change terminals with children and checked bags. We would rather ticket a longer layover than a “minimum connecting time” fantasy at 17:00 on a Friday.
The other airports
Burbank is a gift if you are in the Valley and flying domestic. John Wayne serves Orange County with a curfew personality. Ontario is inland and useful when LAX fares are performing a circus. We will not rebrand SAN as Los Angeles.
Pacific and transcon
LAX is a Pacific springboard (SYD, AKL, NRT, HND, ICN, TPE). It is also a transcon factory. Combining both on one ticket is normal; combining them on two cheap tickets is how people explain themselves to a gate agent.