Probably depends on the person's goals, for example if they want to get ranked GD's they will spend their time mapping for people who they think could rank a map.
Also, modding new mappers is a lot more involved than if you were to just mod rankable sets, a lot of new modders think that modding new mappers will be easier, but its really easy to give bad or useless advice to a new mapper, or overwhelm them with everything you think they did wrong. Just nitpicking certain things like you would for a better mapper that's trying for ranked wont really help them much either. Some people will find that extra effort just not worth it for them (plus its not fun to tell people their map sucks). Personally on the rare occasion I open a mod queue I try to give one or two broader concepts for new mappers to focus on improving for their next map instead of just ignoring them.