L.A. is the pinnacle of the entertainment industry and one out of every 3 people living there are wannabe actors, musicians, comedians, film makers, directors, script and TV writers, models. It is overcrowded, limited space, and primo real estate is a hot commodity.
NYC is the east coast parallel of L.A.
No big mystery, people flock to the places that incorporate their interests, personally, work related or recreationally related.
I live on 5 acres in the Sierra foothills because I want space, peace, privacy and farm animals for pets. Not too many apartments in L.A. that would let me put a kiddie pool on my balcony for my geese. lol