Second, those pointless activities are what we're saving time for. I want to get more work done, and retire sooner, just so that I have more time for my pointless activities. People who don't begrudge every minute they spend in a car, in my view, are failing to maximize the leisure time that should be their chief goal in life.
You can also make other choices that reduce your 15min to begin with. (If the small difference there makes important changes in your life)
> "my 5 min is so important, I'm willing to risk someone's 60 years" (scaled to thousands of people).
The scaling matters! Boston has 1.8 million drivers losing 150 hours in traffic per year, according to https://inrix.com/press-releases/2019-traffic-scorecard-us/. Imagine that all of that traffic was caused by our desire to save a single human baby. 270 million hours lost to save 700,000. Would you agree that's not worth it? That probably those 270 million hours would produce enough economic output to save a different baby instead?
To me, a 75% increase in travel time is high enough and 35 mph is slow enough that I think everyone's 15 minutes is, in fact, worth risking someone's 60 years, once every couple of years. I could be proved wrong about the math, but it seems to me it's mostly an argument about risk tolerance.
In the real world 20mph puts a cap on your top speed only in the few instances you could possibly go that fast. Factor in lights, queueing at rotaries, slowing for emerging traffic, slowing for and then going around cyclists... ad nauseam