For a good portion of the Clone Wars conflict and the animated series chronicling it, most of the Jedi wear pieces of clone armor. The likes of Obi-Wan Kenobi (James Arnold Taylor), Plo Koon (Taylor), and Mace Windu (Terrence Carson), to name a few, put on chest plates, gauntlets, legwear, and more. In-universe, the reason for this simply comes down to the fact that Jedi robes alone don’t offer much protection on the battlefield. These Jedi hadn’t previously spent time on war-torn worlds going up against countless gun-toting enemies, so proper protection was essential.
Continuing this line of thinking, the minds behind “Star Wars: The Clone Wars” were wise to give Jedi clone armor for narrative reasons. As Windu (Samuel L. Jackson) famously states before the Clone Wars begin in “Star Wars: Episode II – Attack of the Clones,” the Jedi are peacekeepers, not soldiers. However, the conflict requires them to become soldiers since they want to contribute to the continued sanctity of the Galactic Republic. Their adoption of clone armor pulls them closer to the troops they command, trading in their status as simple keepers of the peace to be regarded as Jedi generals across the galaxy instead.
Even though it likely served the Jedi well, part of the way through the Clone Wars, the majority of those on the front lines leave their clone armor behind. This is never fully explained in canon, so we’re left to wonder why they went back to simpler robes after a certain point.