[Maxion]

There's a lot of dplyr code out there, and a lot of people who know most every part of the tidyverse by heart, making breaking changes like this so far into a frameworks life would cause a lot of unnecessary work in re-coding old code as well as requring people to re-learn syntax.

IMO for such a small adjustment the benefits don't outweight the costs.

[hadley]

Yeah, that's my current position. It's possible that we might be able to add it in optionally (by adding a new `.by` argument to summarise and friends), but just the analysis to determine how it would affect existing code is a lot of work.