Even thought this might seems like a dumb question it is not. Let me give you few example:
1-why try new new food, if you can have pizza everyday
can other food have other flavors not all taste like pizza you might prefect one flavor over the other each food have it's own flavor giving you a reason to try it.
2-Why bake your own pizza, if you can just order some.
because on option is cheaper that the other, baking your own pizza will allow you to put whatever you want in it while ordering a pizza will give you the standard pizza that the restaurant deliver to others.
-that's true the market is so repetitive new songs are based on older songs new story are an improved version of an older story even movies.
but in each new story/movie/song that it introduce something new making it somewhat different from the older version improving it.
now in my case i can't compete with AAA WW2 games my issue here that i can't introduce anything new making it a special from the other WW2 games this way there's no reason to play my game while you have another better WW2 game.