Bengals are notoriously cheap, and they do have some cap room (about $15 million), but there's already speculation that Joe Burrow is going get a record breaking contract:
https://www.si.com/nfl/bengals/gm-re...0last%20season
Burrow is eligible for an extension after this season, and the numbers that are being thrown around are 5 years for $275 million ($55 million AAV). So, not hard to see why the Bengals want to avoid long term commitments for other players right now. Guessing they are hoping that Bates will agree to a one-year deal at the franchise tag number ($12 million+), but if Bates refuses to agree to a one year contract and if they can't find a willing trade partner, the Bengals have the type of stubborn front-office that would just play chicken for the rest of the season. As Ph noted, the Bengals did draft safeties, but if they want to make another Super Bowl run, relying on rookie safeties is probably not the way to go.