Removing fully-merged branches

Hello!

Permanent issue popping up in our team is removing local branches which were fully merged. 

I know there are command chains doing this job usually starting with git branch --merged followed by grep and ending with git branch -d but my point is why such functionality isn't in git client already when he has all pieces of information already and ability to do all of that. Maybe I am missing some reason behind that but to me it looks like missing feature.

Thank you for your answers,
Vojtech Vladyka