One of the biggest shortcomings of the MSFS SDK is the inability to fine-tune traffic patterns at complex airports like KSFO. At this particular airfield on a typical day, the 28's are (typically) used for widebody takeoffs, while the 1's are used for narrowbody departures. At the same time, the 28's are used for arrivals.
This currently isn't possible to do in MSFS since ATC decides the traffic pattern solely on wind direction. This means you may see departures on the 19s.. which is exceedingly rare at SFO.
We recommend you fly online, on networds such as VATSIM.. or use an addon such as PSXT which inject live traffic. Using default MSFS ATC is not recommended for immersion and accuracy.