The military, at the end of the day, is a tool (famously, another tool of diplomacy). Either it's useful or not. Likewise finance is a tool (fundamentally a service industry like gardening or medicine). We support it because it helps finance business, helps people manage their pensions etc. Sometimes sidelines are useful too (DARPA, gun hobbyists, weird financial instruments that increase liquidity for everyone).
Yet lately the ends have been forgotten and the means elevated. The recent US proposed budget suggests increasing expenditures but there is no discussion as to whether that would be useful or not (and thus whether the increase is unnecessary, too big to even too small). The same problem has emerged in Finance: the point of an financial instrument is the instrument itself. HFT that skims a bit out of the transaction (thus is worse for the fundamental buyer and seller) is considered good. etc.