Why the Perry class was not rebuilt into a premium combatant

Why did the US Navy not heavily modernize the Perry class and its missile launcher for service deep into the twenty-first century?

Because the Perrys were quantity escorts built to a lower price and hull-life expectation; turning them into premium ships would undermine the procurement logic that made the class useful.

The Perry class supplied the US Navy with capable escorts at a price that allowed construction in large numbers. Arleigh Burke-class destroyers occupied a different price and capability tier. The frigates' expected hull lives also limited the appeal of extensive rebuilding for service far into the twenty-first century. The comparison with sailing third rates is about acceptable capability in sufficient numbers: a ship could contribute greatly to fleet strength without matching the most powerful individual combatant.