According to Blizzard, “We wanted to give players the ability to switch between the two options freely, so our UI needed to be unified enough that swapping hardware inputs on the fly wouldn’t throw people completely off kilter. A unified UI means our layouts are more grid-based for ease of navigation, but it doesn’t necessarily mean an identical interaction flow.”
Diablo was primarily known as a click-based action RPG, but when Diablo 3 launched for consoles, Blizzard had to reinvent the game to support controllers. Many reviews of Diablo 3 for consoles have been largely positive so it’s not surprising that Blizzard would give PC gamers a similar experience by allowing the support for game controllers.
Whether or not you take Blizzard up on their offer is entirely up to you, but at least the option is there. That being said, this decision makes sense. Previously, Blizzard stated that they are aiming to support cross-platform play, so by introducing controller support, it should help to level the playing field a bit and make it a more consistent experience.