Forum OpenACS Development: how does the Intranet module "naturally" need apps mounted under apps?

I used the Intranet module only a could of times under ACS3.3 (I think), and it was quite nice. I also saw some dream fragments about how the 4.x Intranet module was going to be really well done with sub-sites and portals, etc.

But the subject question still evades me. If you had an integrated set of applications (e.g. ttracker/WF), why could they not be mounted cleanly in a sub-site (or a sub-sub-site)? Alternatively, how is it a more elegant design (to the users or to the programmers) to have its sub-apps mounted under some main app?

(Actually, I wanted to understand this!)