If a task is easy, then there's no sense of accomplishment when you've completed it.

100 Years ago Typhoid ravaged the US and caused thousands of deaths. If you survived it, you were one of the lucky few and you would celebrate your near-death escape. Now, if you get Typhoid, you can take a few pills to cure it. No one celebrates surviving Typhoid anymore, because there's no difficulty or hardship.

So all that is to say, if we made the whole game super easy and trivial, it wouldn't be as fun or interesting.

And yes, I just compared video games to a bacterial infection!