And these incentives for the beast tribes are also probably in there so that people even do them. Just like Eureka has massive amount of items behind it and we do know from people on the forum that some only went through there to get these rewards. This is my point. Before that blue was at least only his own thing, but suddenly they put these rewards (the morbol being requested for quite some time) behind it. Why? If the niche side content is fun enough for those that want it, why would they need something like that? Maybe because it was not used as much as they wanted to. Or they feared that maybe people would not do it if there is nothing at the end.
Why also compare a normal job, which is only one in a whole line of different jobs, to something that is bascially side content? Blue is not normal in that regard. You could have compared them if both had been normal jobs and the question would be if blue is used more or less like the rest. But he is not a normal job. Blue is side content released at a time with not much to do. So of course out of curiosity (being the first limited after all) people might simply try it out even if they normally dont level other jobs. And its even really easy to level that one. (Also you compare a lvl 80 job which might have needed to play through whole expansions and many hours, to a job at lvl 50 which is done in hours.)
My point with the lucky bancho was: Only half of the people that actively played the game were even interested in starting the job. And of those that did not even half of them reached lvl 50. Not sure how you got that the majority of it who picked it up got it to 50. 46.3% (EU) started it, 17.8% (EU) reached 50. That is not even half of the people. So the majority that unlocked the job did not even play it to max level. Only the JP players had at least half of those that unlocked it also getting it to 50, yet they are known to try out everything and even there quite a few people did not play it further. (With a job that can be easily leveled to max in a few hours). That means only like 17.8% even were able to test out the exclusive new content for Blue. So yes 17.8% is the minority of the playerbase. Which can be fine if that is what SE wanted to have with this. (Even though they probably have no idea how many of those 17.8% in the EU even enjoyed it) But seemingly they now put in incentives for people to play it. And the completely new content (carneval) barely got any updates while most of it was put into a party finder to do old content..
That too is a problem. How do they read their data? Best would be to sent an ingame survey to anyone and question them about it. Because if something is new and people have not much to do, they often just try it out. And if you can level that new content to max level in a few hours and most drop it afterwards, its not really that successfull imo.