Because getting accepted in reputable signature campaigns(and to actually earn merit to get a higher forum rank) requires a good amount of knowledge concerning bitcoin and cryptocurrencies in general. If you don't have that requirement to start with, then forget it.
Do not be hypocrite. We are all here because we want to earn money, money is the reason why we keep on working hard in any aspects,
Not totally. If you browse threads a bit, you're going to see a good number of people(even high ranks) that doesn't promote anything. This is a forum to start with, mainly used for discussions. The money is just a bonus.
You can also read some of the answers in this thread:
https://bitcointalk.org/index.php?topic=5228873.0