Part of the appeal might be that some company provides it as a service. You can distance yourself from the need of spinning of a docker container running it, yo

Part of the appeal might be that some company provides it as a service. You can distance yourself from the need of spinning of a docker container running it, you don't have to go through all the update notifications every week. Makes it seem more like a person than an appliance. Open source might not be very appropriate for this. (And it wouldn't help for the company to use an open source product, because if they're in charge of the infrastructure, re-configuring it to use the filters is the problem and could still happen even if they use the open source software title.) Basically, open-source is a specific solution to a somewhat narrow problem, and not a cure-all for everything bad that happens in technology.