Why only honey bee collects & store honey?
Many different bees also make honey, not just honey bees (Apis species). There are carpenter bees, bumblebees and as Geraldo said, there's honey pot ants.

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.