Comma Controversy

There's a punctuation controversy that pertains to commas, and the question is, which of these is better:

I ate bread, cheese, and grapes.

I ate bread, cheese and grapes.

I probably vary between the 2 patterns, myself. In elementary school I learned the first pattern. In high school I learned the second. And now I kind of think the elementary school pattern was better.

But, the whole thing is illogical. After all, the real question is why does English mix commas and "ands" when constructing lists?

Either of these would be more consistent:

I ate bread, cheese, grapes.

I ate bread and cheese and grapes.

But the odds of a natural language being perfectly consistent
are distant.