As a software architect, you will be involved in obtaining buy-in and making decisions with your development team, customers, management, and other stakeholders. All of the individuals involved in making a decision may not be in agreement initially, so having negotiation skills is useful.
Negotiating is a way to settle differences, and a successful one ends with an agreement that is acceptable to all. In some cases, a compromise is reached to settle a negotiation. A successful negotiation is not just about achieving the best outcome from your point of view but also about seeking a result that is fair to everyone. You want to maintain relationships after a negotiation is over and there should be no surprises when the final outcome of the negotiation is reached.
A number of soft skills are interconnected, and improving one will help you with others. Having communication skills helps with negotiations and having strong negotiation skills is part of leadership. In order to be a good negotiator, you need to be a good listener, communicator, and collaborator. It also helps to have good interpersonal skills. No matter what your personal traits, improving your negotiation skills will come with more experience.