Think of it this way, a company creates an instance (kbin or lemmy). Then they create a community for each of their products (someone mentioned blizzard creating a community for wow). Now, they have this official place for people to talk and the company can monitor it. This means if someone has problems, they can jump in and help them resolve it.

It also means that a company could delete the same posts they don't like, but it's the fediverse, so Blizzard's WOW community isn't the only WOW community. Once they start pulling this shit, their reputation will be pulled down on the other communities.

So, they can delete the spam posts that pollute the community (good), and work with people to take care of problems (good). They could also delete the posts of people who are having problems (bad), but once this happens it would be noticed and posted about elsewhere.