What do you mean? The only reason this didn't exist is nobody did it yet. It doesn't contradict "do one thing and do it well".

For me, the problem isn’t that it doesn’t do one thing well, which is clearly does, it’s that there are no other tools to process trees.

So it fits well with the UNIX ethos of a small tool doing one thing well, but not so much the concept of pipelines, which is closely related.

Obviously not this tool’s fault.

I does take advantage of pipelines, as long as it is on the end. You can use awk, sed, cut, sort, grep and a hose of other tools to massage the data before it gets put into graph form.

To become the front-end of a pipe requires that its or some other hierarchical format become an effective standard shared by a number of tools. It can happen.