Your "can maintain" for those old submarines amounts to "can maintain something which was originally designed to last for several decades, with a high-trained full-time crew, regular major maintenance, and a supply chain for spare parts...and all the billions of dollars which those non-trivial details cost".
Vs. those old rockets were designed to be one-shot expendable stuff. Plenty of them are on public display at museums - you could ask the museum staff about how many $$$/year they have available in their budgets, to keep the rockets in operational condition. (Hint: $0.)
Or, you might want to check out the YouTube channel for the USS New Jersey (historic WWII battleship, now a museum) -
- where their curator often talks in gritty detail about vast differences between "operational warship" and "keep afloat and open as a museum". Note that the something-million dollars which they are currently trying to fundraise - for some bare-minimum drydock maintenance - is small potatoes compared to the cost of a single new F-35 fighter.
Vs. those old rockets were designed to be one-shot expendable stuff. Plenty of them are on public display at museums - you could ask the museum staff about how many $$$/year they have available in their budgets, to keep the rockets in operational condition. (Hint: $0.)
Or, you might want to check out the YouTube channel for the USS New Jersey (historic WWII battleship, now a museum) -
https://www.youtube.com/battleshipnewjersey
- where their curator often talks in gritty detail about vast differences between "operational warship" and "keep afloat and open as a museum". Note that the something-million dollars which they are currently trying to fundraise - for some bare-minimum drydock maintenance - is small potatoes compared to the cost of a single new F-35 fighter.