A startup, like any new business, is inherently risky, and you’ll want the venture to be as financially and legally secure as possible. But more than that, it’s kind of your baby. It’s something that you have created, and obviously you don’t want someone taking that away from you.
So it seems to make sense to want to make every potential investor you show your work to sign a non-disclosure agreement (NDA). It’s meant to keep an investor from having the ability to pass off your hard work to someone else and cut your competitive advantage.