In Divinity, characters were 2D, so each different type of equipment required its own set of animations. Since the characters in Beyond Divinity are 3D, there can be much more variety in animations, and different equipment can be modeled with lower file sizes. This has been discussed a bit in various interviews (see the
Announcements forum /
Beyond Divinity FAQ).
The only auto-equip that annoys me is equipping shields when you are using a two handed weapon.