I don't think people should level jobs if they don't want to.

I leveled seven jobs on my original character. I enjoyed them. But as my taru, I don't really want to do it again. So I can completely understand those who want to stay with one job.

However, if you want to stay that one job, it becomes your responsibility to get the things you want. People shouting need specific roles for a reason; all the other roles have been covered, and it's those few remaining jobs that they need to do the activity.

Even having the job at 90 doesn't mean you'll get invited anyway. I've lost out on many shouts for black mage body seals even though they needed a black mage, because someone else sent the /tell first. Having a job does not guarantee success.

Starting the shout does not guarantee success, nor does having a linkshell that does the activities you enjoy, but both of these will increase your odds much better than sitting in Jeuno, waiting.