You get a whole lot more data with 32 bits for editing to avoid quality loss with extreme edits(not many tools to do that though) as well as possibility to externally do compositing with render passes. Render passes cannot go through any color transforms for them to work properly - they need to be linear values and only after compositing to go through color transforms so you would run into issues if you did it with other formats or lower bit depth. Also you can do color grading outside Blender with the whole data coming out of the render process even though 16 bits should also be really enough for that in vast majority of cases. It is a way to save the whole data that render process generates unchanged. And on top of that OpenEXR format is just amazing as well - see: https://blender.stackexchange.com/questions/148231/what-image-format-encodes-the-fastest-or-at-least-faster-png-is-too-slow and https://www.exr-io.com/features/ It supports Cryptomatte and you can use it in Photoshop! That alone saves me hundreds of hours of work literally.