[mlindner]

Note that for the Space Shuttle, the external tank was large proportion of the fuel-carrying capacity of the vehicle, i.e. "most of the rocket". And for the solid rocket boosters they were not fully recovered as they ejected the rocket engine bell just before impact with the water which sank to the bottom of the ocean on each launch.

Additionally, solid rocket boosters are some of the hardest things to re-use as the process of re-filling them is more like re-manufacturing them than actual true re-use. The sections (they had 4 sections) need to disassembled and refilled with the epoxy that is the solid rocket fuel. They were additionally made of steel rather than aluminum so were not substantially valuable components to recover versus the high end aluminum alloys in the external tanks.