Plex for example starts many transcoder instances within a single container for scalability. You don't _need_ to scale at the container level.
There's pros and cons to each approach, but for the self-hosting crowd keeping the deployment simple may broaden your audience.
A good example I have experience with is vaultwarden: people use it because it's a single container deployment as opposed to the complex and resource intensive setup bitwarden provides.
> We're not afraid to bring in additional containers when it makes sense
That is one of the last things I'm thinking about when I choose a media organization and streaming app, and if I do think about it, having more containers is a red flag more than something that sets my mind at ease, because of that added complexity. I experienced this with Photoprism when I wanted to customize it a bit, because I then had to figure out the roles of the containers and which containers did and did not need the customization bits I was adding, etc..