As a data point, I give my interview candidates the option to sign an NDA.

The only benefit is If they sign I can use customer names instead of generic descriptions (e.g. "large bank" or "telcom provider") and I can show product interfaces.

Personally I thought an optional NDA strikes a good balance, but I've been surprised at how many candidates just sign NDAs automatically. We communicate that it otherwise has no bearing on their application but I suspect some believe that it'll increase their odds.

I believe there is a lot of ignorance about NDAs, in particular by people who just default to NDA'ing all external parties. Doing a lot of NDAs can be helpful in creating a legal record that you communicated with another party.

Enforcing an NDA is more difficult then a lot of people think. If you have a legal department you can threaten to sue an individual for anything including breach of an NDA and in that sense it can be effective. But the only times an NDA has been enforced in my working experience is when there is real theft of intellectual property and you don't need an NDA to prevail in that situation.

https://www.acc.com/resource-library/issues-enforcing-nondis...

Even if you say not signing has no consequence a candidate might not be so sure and see that as a trust/loyalty test.

Possibly a naive question, but it's not obvious to me why you wouldn't sign it? It just means you can't share anything you learn from the application process, right? Why would you need/want to do that anyway?