Cars have annual production runs in the tens to hundreds of millions. There were six shuttles built (one a replacement). Keeping production facilities upon and staffed to create one or two craft per decade was impractical.
Similar arguments apply to military aircraft: the last B-52 was completed in the mid 1960s. Dies and machining for the SR-71 Blackbird were destroyed after the initial production run was completed. Aotomobile production and economics simply don't apply.