There are some veteran members here who are not interested at all in earning merits: they are well known already, connect from time to time and don't participate in any signature campaign, so they don't give anything for ranking up.
Merits will help you gain credibility as a newcomer and will give you access to paod campaigns if that's what you're looking for, but it is not mandatory to "secure your account" in the traditional sense of the sentence.
Additionally, it's important to note that earning merit is not by showing interest. As far as you worth it, you will definitely get it. Showing interest in merit is what keep it far from you even because you'll be desperate and probably end up obtaining it illegally. When you worry less about it, it comes to you when you are focused and doing what are expected of you.
Yes, you are right, but not in every case. I know a few members who took the ranking up as it was a race or competition, to the extent to say "before the new year I'll be Legendary", and manage it (although a few of them almost disappeared after the achievement
).
I have always criticized that behavior/motivation to rank-up, and I think that my case is just the opposite (merits came more easily after the 1,000), but now I am less critical and as long as they don't do harm everyone is free to choose the method he/she prefers.
So we can make here a little recap: ranking up is positive in terms of recognition in the forum and participation in paid campaigns, although it is not mandatory since some members are well known and valued here even when they're just Full or Sr. Members, and some others made from a career to a fortune with the knowledge they gained here, no matter their rank.