Because you are trying to see and hear spirits. The ability has always been there but since it has never been used until now, it has basically been laying dormant in your mind un-acitivated.
You have to activate by practicing as much as you can. Just going into the theta/gamma sync, doing relaxing breathing exercises, meditating to open your ajna chakra, those things will bring you one step closer to this because they tell your mind you are accessing an ability you believe is there when your brain would normally say, it’s not there because it’s not real. Just fight thru that.
And another way to become aware is to look for signs all around you. Until you can see and hear spirits your answers will come with you seeing the same name or symbol repeatedly, hearing a sound too often to be coincidence, finding that when online you keep accidentally stumbling on websites about one particular subject even though you weren’t even searching for that subject, like something keeps leading you to that subject. The communication may also come in dreams so look for any recurring patterns in your dreams, anything that stands out more than usual. This will train your brain to start recognizing signs in mundane things, which is admitting to your brain that what you’re trying to do (see/hear spirits) is real and will work. It’s teaching your mind not to dismiss anything that seems unreal to it.