"You added a client in the same space? Or their competitor?" These are exactly the reasons they want, and are sometimes justified in wanting an NDA. It depend

"You added a client in the same space? Or their competitor?" These are exactly the reasons they want, and are sometimes justified in wanting an NDA. It depends on the domain you are working in. But you are essentially saying you don't want to work in the domains where this is standard, if you say you won't sign a NDA regardless of the NDA contents before a project discussion. My experience is generally the closer to the 'metal' the program is going to be running the more likely there will be a NDA before any details are really provided to you. And to me these can be extremely interesting areas to work in, for instance I would expect this to be the case with most avionics related companies.