In Pathfinder (and possibly 3.5, I'm not sure), Druids get an Animal Companion as a class feature. Rangers do as well, but their Druid level is equal to that of their Ranger level -3.
In D&D 5th Edition, Druids do not have an Animal Companion, only Rangers do.
What was the designers' thinking behind dropping Animal Companions for Druids and making it only available to Rangers? Is there any dev commentary available on the reason for the change?