All the parishes I have attended have a dim light in the penitent area, which makes sense.Some people carry a little list of written sins so as not to forget any, and they need enough light to be able to read it.
Perhaps when you mention light,you are thinking of bright light.

True, the light is low voltage,only enough so that you find your way and where to kneel down.
I could not imagine a confesional pitch black as the ones you go into.
I have seen confessionals that have the priest inside a cubicle and the penitent kneels down outside of it Again, the priest can see you, while you could hardly see him.
Some people may feel intimidated to see a clear close up face there, and prefer to imagine they are confessing to Jesus through a ‘generic’ intermediary, not so much a specific, individual priest.
But I can understand that churches vary, and the ones you go to may feature the priest.