Because a country is an immovable plot of land surrounded by other countries with different motives.

An individual and a company can pack their bags and leave. The actual country cannot. They must defend themselves from attack, sabotage, subversion and espionage.

To be clear, I'm not saying holding gold is the right thing to do. Gold can be seized and stolen far more easily than Bitcoin. I'm just saying Bukele has a lot more to think about than your average BTC holder.