Friendly reminder of the core problem: medical treatments are all balanced against the risk of what it counteracts.
Undergoing physical and chemical changes to grow another creature inside you and have it damage everything on the way out is pretty risky. Female birth control only has to be less risky than that.
A male has zero physiological risk from impregnating someone. Therefore, anything except a miracle drug with high efficacy and almost zero side effects is going to stall at the trial stage.
On another note, that speaks to how safe and effective vasectomies are.
