you do not really have choice since the need for recursiveness depends on the dependencies between packages;
the greatest difference between recursiveness and non-recursiveness is (usually) for the user. as jason mentions if you have recursive deps then you have no idea when you're done downloading things until you've downloaded them, and then downloaded those... and then...
this made my first experience with ubuntu intolerable, i didn't have an internet connection, i was (by definition) a noob, and i had to download packages in windows. in tc that would be no problem, just download one extension, look at the dep list, and grab that list of packages. but even though it's "recursive" for apt, etc (and the user that has to do apt's job) it's really not much different. apt has a database that lists all the deps for all packages, and apt consults this list.
instead of having one great database, we have one tiny database for each extension. it does make tc very simple actually, and although apt may have lots going for it, i really prefer the simple beauty of tc. if we did recursive deps, every time we wanted to tell someone how to install minefield manually, we'd still need to list every dep in one place for them to download, so we'd be using documentation to make up for the new lack in our "package management system" which (as things are) has its own tiny database with all the dep info needed for each extension. (don't underrate this.)