Why are many channels (such as TCM) on fSfS or Freesat but not on Freeview?
Digital TV is broadcast in groups of channels called multiplexes. These carry between four and eight digital television channels each. See:
With the Freeview service it is possible to provide six of these multiplexes to the UK, and it may be possible to add another one after 2012.
On the satellites (at 28.2 degrees east) that are used to deliver digital television to the UK, there are 105 multiplexes, and many more can be added.
What's more, most of these satellite multiplexes can carry more channels than a Freeview one.
This limits the availability of - and raises the cost to provide - Freeview channels.