Long Isl towns?

Why is it that the northern areas of long isl tend to have people w/ higher incomes, better looking neighborhoods, & be somewhat safer? and it cant be b/c it's close to the water b/c thats what the southern part is too. And i have proof b/c just look at towns like bayshore, patchogue, amityville, bellport, central islip, shirley, freeport...ect. compared to north shore towns