Why does the flatness problem (of the universe) present a fine tuning problem? The Friedmann equation can be written
$$|\Omega-1|=\frac{|k|}{a^2H^2}$$
In a period where the universe is decelerated $a^2H^2$ becomes bigger as we extrapolate into the past.
We know $|\Omega-1|$ is today very close to zero since our universe is pretty flat. But if we extrapolate all the way to the Planck epoch or something like that we would have that $|\Omega-1|\approx 10^{-64}$.
Now for some reason, this is said to pose a fine tuning problem.
But I don't see why this is so. Why can't it just be that $10^{-64}$ is something that simply is?
What do we mean when we say it poses a fine tuning problem?
 A: A fine tuning problem is only a problem if we require that the considered model is a good or complete model of how we think the universe behaves.
In this case, it appears that we require the density of the universe to be as close as 1 part in $10^{64}$ to the exact density that will make it a flat universe that will expand forever, asymptotically coming to rest at $t=\infty$. Yet the model considered (the hot big bang model) makes no prediction of why the density should have this very particular value.
If the density lay outside these bounds then the universe would either have rapidly contracted again into a big crunch, or it would have expanded so much that we would not be able to see other galaxies.
It indicates that we do not have a complete model and that something else is required to give us those initial conditions. This, among other problems, inspired inflationary theory. Or, as you say, we could just stop a search for a more complete theory of why the initial conditions were what they were and just accept that this is the way the universe is?
