Because some people where shocked when ck2 ended and ck3 was announced. Those people turned to doomsayers and screamed that emperor will be the final dlc and that eu4 must end due to a similar age to ck2. This resulted in forum newcomers seeing eu5 threads on the frontpage for months and so they now think that a significant part of the community shares the sentiment that eu4 must end soon although it has been the same 5 people over and over (first posters aside)
Your post reminded me of a social psychology experiment I once read about:
A bunch of monkeys with a small shocker on them were put in a room. Hanging in the middle of the room were a bunch of bananas with a ladder/staircase underneath them. Whenever a monkey tried to climb and reach the fruit the whole group was shocked. Soon enough they made the connection and whenever one tried to climb it was attacked by the others.
Afterwards, one of the monkeys was replaced by another. The new member did not about the shocks so it tried to reach the fruit, but was attacked by the others each time. One by one the whole original group was replaced. Even though none of the new monkeys were shocked at all the kept attacking each member that tried to reach the fruit without really knowing why.
I'll admit it may not be related to the thread's topic, but your post just reminded me of that (some details were fuzzy, but that's the gist of it).