Why's that a horrible default? It doesn't happen to match the workflow you use? It matches the one I use. So I can understand it's not ideal for you but they can't suit everyone with a binary default so what makes it so 'horrible'?
So if you merged feature -> develop -> master and remembered to delete feature it would delete develop by default as well...
You're in the minority here. For the majority of software projects branches like `develop` are usually considered "long living" and are not "merged in" when arriving at `master`. That's why we have things like Git Flow [1].
Also an action that defaults to destroying something is user-hostile, so that's why it's a big deal and thus why GP wrote their comment.
[1] https://leanpub.com/git-flow/readAnd anyway Git Flow still has feature branches that you close on merging!