Anyone who reveals personal technical skills, know-how, inventions etc. to business partners, has to be aware that this know-how may be used and passed on. Furthermore it could happen, that an inventor can no longer apply for the patent, because the invention - in terms of patent law - is not new anymore.
Reaching a non-disclosure agreement, the inventor or holder of know-how does not lose any rights. By this means even a possible future license agreement is not touched; the inventor is still free to decide, wether he wants to conclude such an agreement and on which conditions.
A non-disclosure agreement can also be required for the conclusion of research- and development-contracts, respective cooperations and protection-sales-contracts.