Earlier quoted context omitted.
That’s the authors point. Unless you are an extreme outlier and buying a LOT of small purchase (like to the point you don’t have time to work), they really are meaningless. The big fixed items in your budget really drive everything, housing, medical, education, which have all far outstripped inflation. And the income has remained flat for most people (save tech workers who get great coffee for free).
Sure, the big fixed items drive everything, but they are the baseline. Saving on housing is hard, and saving on medical and education is more or less impossible. If you have, say, a $3000/month income, resulting in a $2000/month budget and you need $1000/month expense just to survive, that's $1000/month expendable. A $5/day latte ends up as 15% of that budget, that it is 5% of your income is irrelevant because you do…
Housing -- do more with less. How many people buy houses (or cars) beyond their means or bigger in size than needed?
Health -- daily movement is a life long commitment (as is finding time for sleep) and has outsized long term health benefits. No this doesn't address the "hit by a bus" scenario, but in terms of some of the most prevalent chronic health conditions it's amazing ROI.
Education -- while there is an undeniable tyranny of geographical circumstances, being able to evaluate using community colleges for prereqs, considering alternatives like trade schools, and taking into account expected lifetime earnings for career path all can play into this fixed expense.