Extremely good point. Small forums self-govern as a community and generally just make money (or take donations) to keep the lights on. With big platforms, you are the product and they want you there so they can monetize you. Pursuant to that, the kinds of content they allow, encourage, and prioritize in algorithms and interfaces will be that which maximizes engagement with the platform rather than the community, and advertisers sensibilities rule in terms of what is allowed on the platform altogether.