I think it also happens because of synthetic fertilizers (and possibly modern genetics).
It's a race to grow as big a product in as short of time as possible which causes the mineral ratios to be different.
A tomato which takes months to grow and ripens on the vine has more time to assimilate minerals than a tomato that is "pushed" with synthetic fertilizers, then snatched off the vine unripened and ripened with ethylene gas in transport.
Standard-sized tomatoes take 20 to 30 days from blossom set to reach full size–commonly called “mature green”; they take another 20 to 30 days to ripen, that is begin to change color.
It's a race to grow as big a product in as short of time as possible which causes the mineral ratios to be different.
A tomato which takes months to grow and ripens on the vine has more time to assimilate minerals than a tomato that is "pushed" with synthetic fertilizers, then snatched off the vine unripened and ripened with ethylene gas in transport.