in my day, so very long ago we had a tuck shop where us kids stocked up on sweets and crisps at school every day. noy a piece of fruit in sight, so yes we did eat sweets every day, and they weren't just for treats, it's just that they weren't given to us by our parents.
i believe schools don't have this any more (?) so parents have much more control over the sweet treats now. i think the odd bit of chocolate is fine, ok, if they were coming home with chocoltae eggs every day i'd have an issue but if it's now and again i think it's fine.
i don't think you can get round kids liking sweets, crisps, chips etc, it's a fact of life, to most people they taste good and for that reason will be regarded as treats. as should other 'nice' things that kids enjoy that are healthier, a trip to soft play, the park, bike ride, a trip to see friends, outings etc.
i don't think sweets are the issue, i think it's the fact that a lot of kids are eating more processed food too often and not getting enough exercise. as kids, yes, we ate crap but were out roaming around, climing trees etc for most of the day, burning it all off. there was so need for organised exercise as such, as were just more active in general. now, its a sad fact of life that my son won't be roaming around climibing trees out of my sight for hours on end so i'll have to put in the efort with more organised exercise.