I found multiple questions about this within several last year:
How to search only unanswered questions with an open bounty ?How to search only unanswered questions with an open bounty ?
How can I search for bounty questions?How can I search for bounty questions?
List previously featured questionsList previously featured questions
Advanced search criteria for bounty questions?Advanced search criteria for bounty questions?
Advanced search option to include questions with bounty among the search criteria and other cool search optionsAdvanced search option to include questions with bounty among the search criteria and other cool search options
Can we get some better bounty hunting tools?Can we get some better bounty hunting tools?
Most of answers boiled down to two ideas:
- Use hasnotice:1 answers:0 closed:0. It's imperfect, but what can we do...
- Go and browse featured manually or with limited filtering options
Why it was never implemented? It sounds like reasonably straightforward thing (and without any obvious downsides)
Update 1
I was under impression that a lot of feature prioritization is driven by community. It looks like people interested in it. I didn't see anybody opposing it, but it wasn't implemented within last 3 years. That's the main reason for my question.