And framing it as 40 minutes saved is kind of missing part of the story, because it's every day. Forever! That in fact will amount to A LOT of time saved. Your employer would care about a 40 minute change in your hours one way or the other; why don't you?
Packed lunches or eating out. Shit coffee further tainted by the lingering smell of microwaved tuna. That feeling that you have to be seen looking busy even if you're not doing anything or just really need a break.
And there's Steve, who's always smacking on gum and humming while he works. You're awful, Steve.
Also, I think some WFH zealots on HN forget that other people may not have the mean, or the space, or the internet connection to have a nice office at home, and have pets or children that can be just as distracting as co-workers.