I think it combination of a few things. No particular order
* more hidden sugar in more things. In the olden days we added sugar to things made our own stuff so we could see the sugar in stuff.
*becoming a society that is more reliant on pre prepared/just ad X ingredient sauces/mixes.
* a huge range of pkt snack that weren't available back than.
*general people and medical professionals becoming more aware of allergies and in tolerances and hyperactive
*our bodies not having a built up tolerance to sugar etc..