Why will nobody stock the S4 Active in the UK?

Hi all, I have a question and I wondered if somebody in here might be able to inform me.

The Samsung Galaxy S4 Active is out now in the UK in a couple of shops to buy unlocked, or to buy on some pretty uninspiring Vodafone contracts (not through Vodafone officially though - this is some bodged Carphone Warehouse deal). I had been hoping to pick one up with Three (for their unlimited data tariffs and their supposed no-extra-charge for 4G later this year) but Three don't seem to be stocking it. Neither are any of the other carriers for that matter.

I asked in various carrier stores and nobody seemed to know anything except one lady in Vodafone who said mysteriously "We won't be stocking the S4 Active as it didn't meet Vodafone's internal tests" and then refused to elaborate. She told me "Carphone Warehouse are selling it through Vodafone because the handset is unlocked, but that's nothing to do with us". Similarly I read online that O2 have confirmed that they won't be stocking the handset either.

I wonder if anyone has any news or ideas on this? It seems odd to me that everyone would be shunning such a high end bound-to-sell handset as this. What am I missing?