[PKop]

Firebase has this presence feature as well.

Also, "fully owning" everything isn't a selling point for everyone. Some don't want to own the uptime, manage infrastructure devops etc. Serverless/managed services have their use cases.

Small teams, individual developers, bootstrapping an app quickly, running a web app with no servers to manage... Often times much more valuable capabilities than being able to reimplement to functionality already availabile to you for very low cost.