For those who know photography, what are the benefits of having a manual function on a digital camera? Nothing bad?

Generally speaking, the manual functions mentioned by dc are mainly manual focus and manual exposure. The function of manual focus is that for example, when taking snapshots or shooting in dark light, you can set the focus in advance and press the shutter to shoot without having to Auto focus. Controlling the focus point can also get a specific range of depth of field blur. Aperture priority in manual exposure can control the depth of field, and shutter priority can control the shutter speed when shooting fast-moving objects or getting blur effects. These are fully automatic modes It can't be done. But you can take good photos without the manual function. Which one you use depends on your personal habits.