Lots of possible reasons. Plants grown for sale, especially those grown for sale in flower, are grown in absolutely ideal conditions. Sometimes the transition to the real world can shock the plant, especially if the retailer (or purchaser!) hasn’t handled them carefully. They do need some basic care when you bring them home, check if the soil in the pot is moist and put in a sheltered position for a few days. It may have been that they got more sun that they were used but this usually results in leaf burn or curl rather than bud drop.