the default space between nodes is very large, hence you do not see much when displaying a significantly large hierarchy. see picture for example : to be able to read nodes label, you need to zoom in so much that you only see a couple of nodes and you loose the visualisation of the hierarchy. manually move all nodes closer is a drag...

imho , a smaller default would be more efficient (can not think of a context in which it would be inappropriate to have node closer to each other)

If default cannot be changed, a slider that would allow users to adjust space between nodes would be very helpful