There are countries where there is no army, or it is symbolic. But all these countries are either not truly independent (like Monaco), or "no one needs it" (like any other Nauru-Palau). And - a general point! - they are all very, very small.
So, by analogy with the lock on the front door: you don't have to put it if you have nothing to steal. The army is needed by those countries that have some valuable resources and have no desire to dance to someone else's tune.
It depends on the neighbors. In the vicinity of the Russian Federation or, say, Pakistan and Afghanistan, such a country would simply cease to exist (it would be annexed, or lose its independence, or be seized by bandit formations from neighboring territories, etc.). Surrounded by more civilized neighbors, abandoning the army is quite possible - such countries really exist.
Officials prevent this by all means.