Altered tunings can be one of the most fun and rewarding elements associated with the guitar. Specifically, the ability to change the tuning of some or all strings in the pursuit of finding new chord shapes and evocative progressions is really inspiring. And inspiration is what we all crave when playing and writing.
It’s common to associate 'big change' tunings like open G (D G D G B D) with slide players, but it has also driven some of the most famous non-slide songs in rock and blues. Two fine examples are The Rolling Stones' Brown Sugar and Jumpin’ Jack Flash.