I too am skeptical- except in extreme cases. Maybe if it's some sort of mindless bullshit site that I'm not really interested in I would leave it if it didn't load in, say, 5 seconds. But I don't really give a shit about the bullshit web. Life would be better without that anyway (except, of course, for companies who make a living selling ads on such sites).
But if somebody's leaving a page that has content they need because it doesn't load in 1 second, then I'd say they're a dumbass.
- Mobify found that decreasing their homepage's load time by 100 milliseconds resulted in a 1.11% uptick in session-based conversion
- Retailer AutoAnything experienced a 12-13% increase in sales after cutting page load time in half
- Walmart discovered that improving page load time by one second increased conversions by 2%