[smallmancontrov]

Yeah but they clearly didn't do a very good job on Earth so how systematic could they be?

Don't get me wrong, it's a wonderful premise for a book which can simply mobilize a plot device to brush this problem aside. However, if we want to bring the conclusions back to reality they have to undergo a customs inspection which flags said plot device.

[atq2119]

The solution is that the probes were built by a long ago technological civilization on Earth as a desperate measure in an interstellar war.

The probes are out there and were programmed never to come back to Earth.

[smallmancontrov]

That's a solid plot device and sounds like a fun story! It definitely doesn't pass the customs inspection for use in speculation about the real world, though.

[atq2119]

FWIW, it's part of the plot of Andreas Eschbach's Lord of all Things. (IMHO one of his weaker novels, but weirdly one of the few that were translated into English)