I doubt kids in the past would hear from their parents such bullshit like "you can't dice these eggs with this, it's for dicing onions", etc.
It's not consumerism it's specialisation: with the advance of sedentarisation and techno-industrial might, we can afford to go beyond one tool doing a bit of everything not very well (e.g. shave and punch holes and cut food and …) and instead use plenty of tools which do one job very efficiently or conveniently.
The price difference isn't particularly justified, but presumably "face razor" and "leg razor" doesn't sell as well.
Not to mention phones are really quite good at being mp3 players and GPS devices and cameras at least for the average person, so the tradeoff is not big.
I suspect the reason most archaeological finds are attributed to a single purpose is a much simpler one: it can sometimes be hard to derive an accurate description for a lot of tools when you're only looking for a single use. Trying to find multiple uses is therefore going to be an order of magnitude harder. So you therefore go with the most easily identifiable use case.
I bet the ancient ones had the same problem when someone used a small shard of rock for a job that a larger shard was clearly better suited for! ;)
They then picked up a wedge shaped chunk of stone used it as a hand axe for a few minutes, took a chunk that had cracked off it to use as a knife, smashed it again to make a scraping tool and on and on.
I think it's just hard to understand how tools in the past were used.