It centres around the 'Rocket goes up' bit
Going to a higher orbit takes more energy, and no manned vehicle can go above about 800 km right now. Since there is only the one (Soyuz) that can take people into space and that's it's range on it's normal launch platform. Back in the shuttle era the limit was even lower, since the shuttle weighed so much, and had a very delicate reentry window, almost no missions went over 500km(Hubble was the highest, @ 620km). For reference Geostationary sats live at about 35700 km.
The Falcon Heavy will be able to launch a Dragon 2 into that orbit and the SLS will be able to make that as well, but the SLS is looking at 1-2 billion dollars per launch so there is no satellite that is worth spending that much to fix.
If DARPA can make it work, and SSL can build these for less than a hundred million, there would be a massive market for this service. Maybe even make the robot refuel-able and reload-able and just have it flit around fixing and fuelling sats for years!