Kent,
Such traffic standards as TIS (Traffic Information Service) provide ADS-B-like services to pilots, but are NOT part of the ADS-B system. TIS is a USA-only system requiring the aircraft to be in a Radar Service Area (RSA) and also have the needed TIS equipment. This pertains to many USA class B and Class C airports.
The TIS-B Traffic on the ADS-B System provides much more accurate traffic positioning as it is WAAS GPS based, not Radar based. Additionally, TIS only functions in the RSA, TIS-B is functional outside the RSA via air-air communications with ADS-B Out equipped aircraft.
Both are good traffic solutions, but the ADS-B TIS-B traffic trumps the TIS only system and would basically offer no benefit over Full TIS-B traffic. One would think if you have ADS-B Out and an ADS-B Receiver, you have better than TIS traffic already. This will be even more evident as we approach the 2020 mandate of ADS-B out. Then you'll see most planes air-to air.
With that said, we will continue to monitor the demand and requests for TIS integration. I hope this helps.