The only time you'd want to use this...
...might be the only time *you'd* want to use it, but it's not the only time others would want to use it.
Streaming live/recorded TV is all well and good if you've got a decent broadband connection, but isn't much good for people with ropey connections or no connections at all, and might not be much good for people with fast enough connections hobbled by download limits.
Then, as you say, *nearly* all Freeview channels can be viewed online. So anyone who wants to watch one of the other channels is going to be stuck no matter how good their network connection is.
At home I've got a broadband connection easily good enough to stream HD content all day long without any fuss, but my mediacentre PC still has a dual DVB-T tuner card fitted (and will be getting a HD upgrade at some point) because it's more convenient for me - if I want to watch something I don't have to think to myself "hmm, which website do I need to visit to stream this show", or be faced with a "sorry, this programme isn't available online" message. Also, since I tend to catch up on some shows on the bus/train/etc, having them recorded in a form which is easy to convert into something my Desire S can play is also rather handy.