Lets say that 2109 has arrived, and a mission has arrived in this far distant system, where a Earth-like planet exists. So as the approach starts to occur....radio reception picks up tens of thousands of signals, and the 'boys' in the craft now realize that this is another civilization.
So they pull out the handbook, and it goes down to a dozen 'rules'. Three key rules will exist....(1) do not make contact until you have surveyed the situation, (2) hide your craft with the use of moons, and (3) limit radio communications.
After a while, you will decide that surveying up-close will be necessary....meaning to send a team into orbit, and land probably in their ocean...hiding your craft there.
This survey may take weeks, months or years, and the do-not-introduce yourself rule will always be enforced.
So you take this whole book of rules and expectations, and it's exactly what I'd expect of any alien visitation on Earth.
Why would you excite folks unnecessarily? Adding to the mess.....you don't want to let them know that you might be 1,000 years more advanced.