"Pages are more often than not hierarchical in nature"
Actually no: pages, and other contents, are rarely hierarchical. When they are, the hierarchy is usually not deep. And when it is, taxonomies are a better solution because they allow for multiple classifications of the same contents. Furthermore, many usability
studies have shown that treeviews are not well understood by most users. That's why Windows has been trying to hide the hierarchical nature of the file system and has attempted to show a small number of top level categories instead.
As for the few content types we have out of the box they are not imposing much: they are those that we determined were used in almost all web sites. They are also not a constraint as the type system is highly extensible.
If you want the admin to surface hierarchical contents, you will have to build that I'm afraid. I can remember getting this request maybe five times over the life of orchard by the way, which should tell you something about how much people really need that
Of course I'm not denying that is what you need, just saying that the scenario is not as mainstream as you may think.