They're not releasing Voice on EOS, in my opinion, because of all the resource problems they are having on EOS. It wouldn't look good to ask people to buy $100 worth of EOS just so they can interact on Voice.

While Steem is a possible solution I would think it's much more likely Voice will either run on a sidechain of EOS created by block.one until all the resource issues are addressed, or released on something like TELOS, which is a fork of EOS, but resource required to interact on the blockchain are much cheaper, and would allow an easy transition once the EOS blockchain is ready.