Isn't scrolling a single docker-compose.yml easier to see everything? I mean, if you want to change anything - you just edit and re-run command.

Personal preference. I prefer a gui for some things. I also prefer to not put all my containers in one monolithic config. It can also automate using configs in GitHub which is nice.

It also provides a nice dashboard of container health across multiple hosts and makes it easy to manage those hosts from a "single pane of glass".

But, personal preference.

I ran a kvm host manually for years. Years. I recently started over with proxmox because it could be exhausting and this is easier.