The purpose of a military is not solely to provide continuity for a currency, it is to provide security for the interests and inhabitants of a nation.
Also, regardless of any morality issues, having a military _creates value_ in a way that Bitcoin cannot. The employees of a military are paid, they spend their wages in the country's economy, they must be supplied with equipment which must be manufactured, those manufacturers & soldiers pay taxes, the enhanced security of a nation makes it less risky for investment and business growth etc etc.