Not to sound all woowoo, but if I'm correct there's been quite a lot of military spy sats very similar to Hubble. These weren't designed to be serviced if I understood. Could it be that the design of Hubble was based largely on these sats, resulting in not too serviceable parts?

I'm not sure at all, as a) I don't know whether Hubble was the first in the row or not and b) Hubble was (re?)designed for serviceability (for example, the yellow grips everywhere)

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