I dont understand why Phase one wont add the feature to display cumulative view of all folders/albums under a parent folder or project.
It's not that they "won't" it's that they haven't yet. I've been doing product management for a few years now and the number one lesson I've learned is that there is very rarely a shortage of very good and useful ideas that will help some of the users. The trick is prioritizing.
It is so helpful to work on some common themes in a high level view and then jump into specific folders/albums to do more specific processing. It is also helpful when culling the images, or selecting for a certain use.
In our classes we cover a variety of ways to accomplish this. I agree the ability to toggle a "show within" option would be more intuitive than those options, but there are already pretty good solutions to this need.
I have asked customer support since V8, they agree to this in principle, but obviously have no power to make decisions.
The vast majority of improvements made to C1 start as a feature request from a user (or prospective user) via a support case or feedback provided to their Phase One dealer. Just because your specific idea has not been implemented does not mean that the idea wasn't heard or that providing that feedback via a support case is without power.
Is there any technical reason that Phase One wont implement it. Is it not useful for other photographers as well?
There can be some knock-on effects for both UI and performance. For example, do you just want child folders or grandchild, or every level all the way down? Do you want to be able to see some indication of what level they are at when you select the thumbnail of an image, and if so how and where should that indication be? Should it the feature be on or off by default?
These are all solvable problems, but in programming it's pretty broadly the case that a major change to the way a program works (and yes, this does constitute a major change) is always more complicated than it seems to the outside.
So keep submitting the support case requests every version, and feel free to drum up interest/support from other users to to do the same. P1 really truly does listen (again, look at the list of features implemented in the last 36 months; they nearly all come from requests made by their core users). If you'd ever like to meet someone from P1 we (DT) have public events several times a year with high level R+D staff (often the head of all R+D who is a super cool guy).