Some statements are expensive to prove. If I need to make a proof for such kind of statement repeatedly (generate new proof $\pi$ for each new verifier), I think it might be a waste of time (as well as computation resources).
- If there is a proof $\pi$ that I generated in a non-interactive way, can I reuse it?
- What problem would cause if I try to show it to several verifiers?
If this proof $\pi$ could still maintain its effectiveness, and does not harm the soundness and zero-knowledge property, I think it would be helpful to reuse this proof.