This is the issue. Relying on private entities to provide (R&D, clinical trials) for what are ostensibly public goods (antibiotic resistant bugs puts every person at risk) brings the real risk of market failure.
The NIH is making some progress on this front.
https://aspe.hhs.gov/system/files/pdf/258516/ProgressYears1a...
It appears that overprescribing existing antibiotics to people and livestock is a leading cause of rising drug resistance, both of which can be addressed by policy changes.