In more ways than one Bengalis and mishti are synonymous. This is Bengal's most prized gift to the World. So much so that now a days sweet shops all over India proudly highlight the fact that they also make Bengali sweets. I can bet if you look around in your locality you will at least find a shop which has that quintessential banner saying 'Bengali Sweets are available here'.
While growing up I never took sweets seriously. I mean it was available every where, whenever I had a craving I could go to the corner mishti'r dokan (sweet shop) and can have my share from numerous types of offerings in every possible size, shape, colour, taste. It was later, much later when I moved to Delhi and found how crazy people are about Bengali mishti. no matter how everyone love making fun of our Bengali pronounciation with excessive stress on the 'O' sound people take Bengali mishtis seriously, very very seriously. and why not this art of sweet making dates back a long long time and needs a lot of patience, skill and finnesse.
As per Dr. K.T. Acharya Bengalis appear to have possess a sweet tooth since time immemorial. It evolved as part of the plentiful availability of fresh milk. The fact that cheese making were never practiced in this part of the world, eventually it led to sweet making either by curdling the milk to get chhana (homemade cottage cheese) or by reducing the milk to prepare khoa or khoya (milk solids). Though initially curdling milk was not considered auspicious. Mainly because Ayurveda never encourages Hindus to take any spoilt food and splitting milk was considered the same.