Because that was part of the Space Shuttle's original purpose, but the reusability and cost didn't work out that way: "The original plan, ridiculous as it was

Because that was part of the Space Shuttle's original purpose, but the reusability and cost didn't work out that way: "The original plan, ridiculous as it was in hindsight, was for STS to be the sole US launcher of all payloads. However, after the loss of the Orbiter Challenger only seconds into mission STS-51-L, US policy was changed to only allow the Shuttle to launch scientific and military payloads that required human presence. This destroyed any economic rationale for making STS self supporting or a revenue generator. The first 4 missions were test flights, so omitting them, you can see that 11 of the 21 "operational" missions before the policy change carried commercial satellite payloads, often multiple, up to 3 comsats per mission. A total of 18 commercial satellites were deployed from the Shuttle. " https://space.stackexchange.com/a/10352 https://space.stackexchange.com/a/10352 The original purpose of the Space Shuttle was to be a highly reusable launch system to make frequent launches (including commercial and govt satellites and space probes) with minimal refurbishment time/cost. That sounds an awful lot like SpaceX's current goals, doesn't it? Yes it had some mission profiles that the current SpaceX fleet can't do (large extended-duration crew missions in LEO, orbiting laboratory, Hubble repair) but there are also profiles that SpaceX can do that Shuttle could not (anything that involves stage 2 going beyond LEO).