To be fair, that is somewhat the current scientific consensus on gravity. It just is. We can meassure it and determine a general constant and calculate with it (and even though some people claim to have understood way more, it is highly debated terrain as far as I know)

Sure, and if we come up with some fancy unified theory, and ask "why" once more, the answer will still be "uh, because they do?."

But they are for real (but with a very different concept of reality).

We think ourselves so advanced. I wonder what big counterfactual scientists believed in the 1900s and 2000s will be laughed at a few hundred years from now.

And, of course, some of that will be libel; e.g. that we thought the world was flat "just like Christopher Columbus's compatriots" [who didn't].