Is a separate CI tool for Terraform needed?

Why are people using Terraform Cloud? I may be missing something, but why can't terraform just be run in GitHub Actions?

I feel that for 99% of companies, a terraform runner fundamentally only needs the following flow:

1. Run terraform plan on every PR

2. Run terraform apply on merge to master/main branch.

3. Handle of concurrency by queuing multiple applies together.

4. Terraform secrets can be handled using GitHub Secrets.

I created a demo repository [0] and it seems to work just fine. What am I missing?