Soma is a fictional drug popularized in Huxley's Brave New World, and used to ritually sedate the populace in seemingly benign but pervasive manner. It's closely associated with with consumerism, in the of form of "feelies" (also from BNW), as Huxley was alive to witness the transition from silent films to "talkies", and didn't respond to the perceived gross spectacle. In my mind, soma is a generalization for all that preys upon human weakness, and for something that is justified, even by intelligent, renowned individuals, via illogicality and appeal to human nature ("it's fun", etc). Rather than consider the value of the intoxicant itself compared to the innate conscious state, you typically see defense of it and claims of its banality and harmlessness. This is cognitive dissonance and justification, nothing more.
The government wins by profiteering either way off of legalization or not. Police states enforcing the war on drugs is profit, and tax revenue from legalization is profit. The people celebrating the current trends as a win are delusional.