Better publicity ?
Part of the reason that the beeb may not be finding much uptake of the 3D service is 'cos they just don't seem to publicise it, from what I can tell. Since I seem to watch most things recorded via the PVR nowadays I *might* have missed related plugs,, but then we have the Radio Times and I'm pretty sure there's little mention of 3D transmissions there either.
Other than Dr Who and the olympics I really don't recall anything being shown in 3D - and that was squirreled away via the red button, which isn't normally (or certainly wasn't a while back) appearing on schedules.
(in the event that I've missed something, I'm sure there'll be someone along shortly to correct me..)