Adding a single small feature doesn't take up that much space, but what differentiates this small feature from another? Why not add that one, too? Therefore only features that provide significant value exist.
What problem does that solve?
Many. You could for instance use it to post a submission when lots of people are online.
Suppose that would just create a huge influx of new submissions though now I think about it.
Does it help to solve the problem of keeping the community from degrading? That seems to be the main thing that PG cares about when adding features to HN. If the only thing it make easier is targeting submissions for maximum karma and visibility, then it seems to me like it would be more likely to damage the quality of the community.