Well it is still a phone after all, what with UMA and baseband processing. You don't need to spend much time at Blackhat/Defcon to realize any true attempts at sealing it up are akin to plugging leaks in a sieve with epoxy. Its far too porus.
Meanwhile if attestation does reduce fraud, the ownability (by the user) of the device is now forfeit due to chasing a dragon's tail.