There's still lots of knob and tube electrical distribution in San Francisco.
Some people don't see any value in upgrading it... hopefully, they're not your neighbors!
Some electricians also have been working with this for a long time and have become inured to it.
It's difficult, costly and disruptive to abandon all the old knob and tube wire.
If your home is already insured the most practical way to upgrade is to
install modern arc fault breakers as possible,
add new code compliant circuits as needed,
starting with the kitchen, the bath and points of heavy use.
Thermally protected outlets as per need
Verify the integrity of the grounding system
Install smoke detectors
We usually recommend to abandon knob & tube incrementally, again this is if your insurance company has no problem with it!
An obsolete electrical system that is giving warning signals should be inspected and corrected as recommended by an experienced professional
Good Labeling! Under the fixture :/
Modern electrical systems are very safe.
