In city traffic of any appreciable density the type of following distance that you can discuss on the internet without getting flak from the holier than thou types will quickly fill itself with cars pulling off of side streets or merging in front of you.
"Your safe following distance is my opportunity." -Jeff Bezos
People who think - I"m more important than you, I don't care if I kill you, as long as you don't inconvenience you.
The law (and insurance companies) are pretty clear on this (at least in Australia) - if you rear end somebody, it's nearly always your fault, for being silly enough and not leaving enough gap.
They have educational campaigns on leaving enough gap (it's meant to be 3 seconds). Things happen, and people have to emergency stop.
It's taught to every driver.
I think eventually you'll get into a steady state solution where you'll be limited to 20mph on a 65mph freeway because that's all the room you'll be given - if you follow the rule of law exactly.
Instead, most bay area drivers keep about 40-70ft between cars when going 70mph. Juuuust enough to react in time to an emergency stop. It's a little silly but it's the only way you won't get cut off constantly. Only other way to not get cut off is to go quite slow and be behind traffic speeds.
So based on this you give us your throw-away "3 second gap" comment, helpfully telling us that this is the law and something something emergency stop etc drive safe?
With an average speed of less than 10mph, and a very dense city, your normal traffic "rules" don't apply here. Don't even pretend you can understand how things are here without experiencing them.
This is trivially true! Otherwise cars would not be allowed on public roads.
When it comes to cars, it's always about tradeoffs and acceptable risk.
FTFY