That is it and in same vain, legendary members contributing to the forum and answering newbie questions is not also obligatory as opposed to what Op thinks. Those regular names we see here daily and weekly are passionate about the forum. It is not easy for some people who were here since 2013, 2014 or even earlier to still remain active. Most of the people who started earlier are no longer here.
It doesn't really make sense for a Legendary member who in 2017 and 2021 has managed to become a billionaire because of his investment would happily spend a lot of time replying to spammers here. They wouldn't because honestly now they would really appreciate the time to enjoy life in all its luxuries. They can stay here for any number of reasons, but I'm sure it's not for something pointless.
I understood that low quality post or spamming that happened somewhere 2018 was a major reason some old users left the forum. I read it somewhere outside and inside the forum. That made me know that it was so bad then. Thank theymos for the merit system and signature campaign, who knows there might not be any old user here today.
Some left due to bruised ego and gross misunderstanding, but as you rightly noted, those early adopters of bitcoin who might have turned billionaires has no reason to remain here except for passion.
Legendary is not the end, it's just the highest rank and every one of them should still care about post quality if they don't want to be called spammer or shitposter.
Anyone that has quality must surely produce quality at anytime, even in slumber. It is not something anyone will decide on when to produce quality and when to do otherwise. Then I understand that old users also care most about quality. That is the spirit.