People sometimes wonder why anyone becomes an editor - why would anyone waste their life reviewing and listing websites and not get paid for it. The general assumption is that most people become editors to get their sites listed but that seems to be incorrect. I don’t know of any reliable measure of the different reasons, but here are some.
Someone may have a particular interest in a particular topic and have already collected sites related to that topic. Being an editor allows them to put that list into the public domain, and continue to develop the list. They apply for the most appropriate category, and perhaps later apply for additional categories.
Some people have varied interests and like the concept of contributing to the public good. They like looking at varied sites, reviewing them and listing them.
There are those that just like the general idea of organizing and categorizing topics. These type of people often become librarians and indexers, and they may do that as a full time job. Being an ODP editor, just extends that ability and interest.
Some only have part time jobs, or are retired, and being an ODP editor is a hobby that stretches the mind. It beats being glued to the TV watching mindless media.
Some people do want to get their site listed, they are not professional SEOs or webmasters, they just have one site for their business, and want to get it listed. So that’s fine, provided they are even-handed and also list competing businesses. They have no interest beyond that single category. Note, that it is not that common, and that a large number of ODP editors do not even have a web site.
It is not uncommon for someone to apply in order to get their site listed, but find out they enjoy ODP editing, and continue on to ask for additional categories and do extensive editing of sites in many categories.
There are of course those who join with ulterior motives, they want to manipulate ODP to their advantage. They join, edit correctly for a while, then start to try and sneak in mirror sites, or tweak descriptions with keywords.But it’s not that easy, an editor starts with one small category and has to work their way up to get additional areas to edit. There are also cross-checks and balances, any editor can see what any other editor has done, and eventually someone will notice.