Why do I dream of places I've never been, and people I've never met? Or have I just not lived that part of my life yet?

I dream of seas uncharted
Forests untouched, creatures that speak different tongues.  
I've flown faster then I could see, soared higher then I could dream. Lived and died through lives till I reached insanity.

Science says its all just sub conscious. what I see is all pre determined, like a program expected to keep things together. Yet why are my dreams  leaking into my daily life. These
Places ive been
faces I've seen
I can't find them in real life.
Or Were they hiding in the sea of heads when I walk the streets,
Or where they sitting right beside me on air plane seats.

So why do I see these places? Beaches on top of caverns, jungles inside of mountains,  cities under water, and you holding my hand as we stroll through the park on a windy day. With you wearing your favorite scarlet  scarf. You smiling back at me as we pass a man playing the piano. Your favorite instrument. you tell me how one day you'll learn to play as well, and I'll be seeing you perform on stage one day. And I kiss you on the cheek because I love how you dream so big yet never fail to include me in it.

Ah yes.
Why do I dream of impossible places with faces I've never met.
Or maybe I just haven't lived that part of my life just yet.