This was my thinking. From the way the author writes, they seem to say, "I would skip lockdowns, in exchange for giving up my 15 extra days of life". If that were the thing on offer, I think a lot of people would say "forget the extra 15 days, I'll not have a lockdown".

That's not what it is though. The question is, would you go into lockdown to give everyone in the country 15 extra days of life. That's what you're trading. Personal inconvenience for strong positive externalities, you can't just think about the part of it that comes back to you. It's a general societal good that you're doing.