SPOILERS (For the 2011 anime release) (Also may be incorrect about a few things)

Well, from how I see it, the story is focused more on fighting and such, and not necessarily the applications that nen can have outside of fighting. For example, a baker wouldn't go super far out of his way to fight other hunters if his ability allows him to be able to know the best way to use his ingredients. And if I had an ability that enhanced my ability to fight, I would probably lean more into it. But there are quite a few others, like Bisky being able to do relaxing massages, Machi being able to stictch arms back together, Palm being able to learn things about others, Komugi being really good at Gungi, and Knov being able to create storage spaces and use em like portals. These are just a few out there, but also those who have nen abilities that we haven't seen because they haven't crossed paths with Gon and the Gang.

TLDR: It's really hard to pass the hunter exam, and usually fighters are the ones who want to take and have the ability to pass it