In Insects, most of flying insects like butterfly etc, diet is sucking honey from flowers. none of them store honey except honey bee. Why so ?
Only honey bees make any great quantity of honey. The other species make far less and it's a different consistency. Honey bees live in large colonies and honey is stored to feed developing larvae as well as feeding workers and the queen through winter. Other bees are solitary except for a few bumblebee species but their colonies are much smaller - usually less than 50. Bumblebees make far less honey. There's no need to store honey for winter as the queen and workers die in late fall. Only a newly hatched and fertilized queen will survive, hibernating through winter underground. Hence, storing more than the immediate needs of queen, larvae and workers would be pointless.
You mentioned butterflies sipping nectar. A butterfly's lifespan is very brief and only sips nectar to provide energy for fertilization and egg laying. Then, generally, they die. Larvae have been provided for already since the eggs hatch on the appropriate plant leaves as their food.
Its a symbiotic relationship nature has established between honeybees and the vast hundreds and millions of plants that depend on them for pollination. Honeybees do almost all of the pollination. You cannot compare the vast proportion of pollination performed by honeybees with all the rest of the pollinating insects combined.
Because of this pollination dependency, nature has provided honeybees with robustness of colony sustainability, survival, and reproduction. The energy density of honey is very high and it has all the nutrients the bee larvae need to grow into healthy robust adult bees. The honey is also a great insulator to help prevent the hive from getting too cold in the winter. Honeybees are the earliest pollinating insects in the spring, right on time for the earliest blooming flowers. Their communal collaboration and communication teamwork in gathering nectar is astonishing, unique, and well documented.
Without honeybees, we would have to do without fruits and vegetables, which is why scientists are working around the clock to figure out colony collapse disorder.