The default texture pack's bow texture is bugged. The punching animation is weird, and the bow texture when in your hand is buggy. Some pixels are invisible, including the draw string and the arrow itself. Some texture packs make the bow completely invisible in the hand. You can see a video on my YouTube channel. DiamondBot. You have to filter to channels only to find it. Should be the latest video.
Duplicate of MCPE-116741 and MCPE-119702