[ithkuil]

It doesn't even have to be likely for it to be a worry.

Imagine there are 1% chances that an encounter with an alien civilization spells the end of humanity.

Or 0.1%, or 0.01%

Now roll that dice for millions and millions of years. It's probably a good idea to switch to communication technologies that don't broadcast your location (and your technological unsophistication). Just in case.