I was reading one of top posts on TIL about a soviet pilot who defected and was shocked at how a grocery store was actually stocked. I've seen quite a few similar stories that speak of the lack of basic necessities during the reign of the Soviet Union. Why did an empire that was presumably one of the top world powers have so much trouble providing and supplying goods to it's population?
The Soviet economy prioritised the building of industrial infrastructure for economic development before consumer goods. In the West, the development of industry and consumer markets happened on a more parallel level, albeit on a longer time scale. The Soviet economy was focused on development and strong growth (which it did exhibit for most of its existence), but it funded this development at the expense of a consumer goods market which grew at a slower pace (though still was growing).
The biggest factors involved aside from that are that the Soviet planned economy took priority on a base of needs of the population above all else. Additionally, the Soviet economy started from the ruins of the Russian Empire, and was miles behind all of its powerful Western counterparts, and was at a large disadvantage from the beginning in regards to economic development. Additionally, it was cut off from trade with most of the world as a state that was antagonistic to Western capitalist states and empires, which forced its development down a more autarkic path than it would have probably preferred. It spent most of its existence trying to bridge this gap and build itself up as an economic power. In that regard, it was reasonably successful, but again, consumer goods took a backseat to industrial development, although the consumer goods market in the USSR did begin to undergo more significant development towards the end of its life.
Development of consumer markets varied wildly across socialist countries. The socialist country that probably had the most advanced consumer goods market was East Germany, which started from a more advantageous point when compared to the USSR.