finch, I think you nailed it for most readers. However, there is a small minority of us that really like that cheap little plastic holster. If it happens to fit well ergonomically, and if you have a penchant for such things, the little plastic holster offers two huge advantages:

First, it is VERY easy to manupulate it very quickly and securely with one hand -- that *CLICK" in and out adds an auditory element to it, as well

Second, as a result of point "first" above, when you receive an incoming call, and you want to shut it up FAST, you can, using one hand -- very unobtrussively, *CLICK* the BB out 1/8th of an inch, and *CLICK* it right back in, and the phone shuts up -- and doesn't ring again! This is huge...at least for me

Just my $0.02