Aside from helping your users be successful with your solutions, you need to build a community for the conversations about your products and your brand to happen in a friendly civilized environment.
Since most of us work in corporate environments, it is not a far-fetched scenario where you get asked: “Explain to me, why do we even need to invest in building a community? Can’t we just have a good Knowledge Base and Support instead?”
If you only approach this question from the standpoint of helping your users with their technical questions, then you really don’t have an argument for deploying a user community platform. If you only want the community there to field questions, spending the money on hiring more technical writers and support agents will indeed bring you more bang for the buck.
Once your product is out there for the world to see, conversations will start happening around it. People will talk about your brand and your products, and their experiences with them. There is nothing you can do to prevent this, and neither should you. Conversation is a good thing.
Just like in the olden days people made friends and invited them up for tea, creating an official space for your users to get together and have such conversations will get you good will from them.
What you (and your hypothetical question-asking colleagues) need to realize, is that your community exists independently of you. The moment you let people get their hands on your product, you have created a group united by their user experience. When you spin up a forums platform, all you do is give that user community a welcoming home, where you get to set the tone and rules of engagement.
If you don’t give them a home, they will go and talk about you on somebody else’s online forums, the conversation will become fragmented, questions will go unanswered, and frustration will build.
The “welcoming” part is also important.
You know the typical internet forum: full of snark, flaming, and other such things that leave an unpleasant aftertaste. Since you want your community forums to be a welcoming and professional place where people can have conversations undisturbed by trolls, some amount of benign control on your behalf is necessary and will be welcomed by the participants. As long as you only police the tone and not censor any negative comments or criticism, your efforts to keep the discussions clean will be supported, and when you are ready to recruit your volunteer moderators, they will have a clear example to follow.