Good question. The rationale behind restriction of most drugs lies somewhere between perceived potential destructive tendencies to society and the individual. Several currently restricted psychoactive substances were well integrated into many societies since before the modern era, but the Western globalization effort/complex can arguably only stand if we allow two drugs without restriction: alcohol and tobacco. Benzodiazepines stimulate the reward pathway and are relatively novel - a combination which could synergize destruction in the aforementioned forms.
Yet they primarily work through a neurotransmitter called GABA (gamma-amino-butyric acid), which ethanol is known to also increase levels of. They are furthermore much more safe than ethanol, as it requires many grams of, for instance, alprazolam (which is active at .125mg) to kill oneself whereas one could undergo fatal respiratory depression after ingesting ten ounces of pure enthanol. The problem lies in ease of consuming pills versus ingesting a caustic liquid. Additionally, benzodiazepines are notorious for inducing a state in which one is severely inebriated though doesn't realize it, causing reckless endangerment like driving under the influence. Alcohol doesn't display this dynamic to such an extent.
They are schedule four drugs though (excepting rohypnol or flunitrazepam), relfecting their similar action to ethanol.
Not every country controls benzodiazepines so much.
One has no incentive to ingest copious amounts of NSAIDs.