Near term, if something goes wrong with those probes, they're a lot easier to fix when humans are lightseconds or lightmilliseconds away than when they're light

Near term, if something goes wrong with those probes, they're a lot easier to fix when humans are lightseconds or lightmilliseconds away than when they're lightminutes or lighthours away - and human personnel can typically do the job better and easier anyway if they're present. Medium term, moving as much industry as possible off of Earth is a vital release valve for mitigating our destruction of Earth's biosphere. No other celestial body (to our current knowledge) has any biosphere whatsoever, and only a small number could even hypothetically support one. Strip-mining the Moon or Mars or Ceres or the umpteen-bajillion asteroids and gas giant moons entails no demolition of rain forests, no extinctions of animal species, no displacement of indigenous peoples. Long term, moving as many humans as possible off Earth permanently resolves the risk of us destroying it. The end-game is for Earth to be a preserve, allowed to heal from the wounds we've inflicted upon it over the centuries.