So far I haven't seen a single streamer revert to ads on Dlive.

Of course not. Potential ad revenue on the Steem blockchain would be a piddling at this time. The value of STEEM is mostly speculative at this point. The value proposition, however, is to become a global advertising and promotion network according to the whitepaper. Should that never come to pass, the whole thing would've been a huge loss for the investors, that is, people willing to exchange STEEM and SBD for money that has purchasing power in the real world. Once Steem grows very large, corporations will be clamoring to get the attention of the masses using it and they will be paying top dollar for it. The blockchain is also a highly scalable decentralized payment system enabling micropayments to boot so that will also be a source of value for STEEM.