I'm surprised that there isn't an automated way to do it.
That was my initial feeling too. When I watched a video or two about it (UV unwrapping), I began to understand why there's so much manual effort involved.
I'm sure you're familiar with different globe projections...
(I'm still really new to UV wrapping & mapping, so I might have the details skewed.)
Some 3D Software DOES have the ability to automatically unwrap your 3D model onto a 2D surface. This works really well for simple objects like cubes or spheres.
But as you can see in the globe example above, going from the 3D sphere to a 2D image could be done in
at least 4 different ways. There are plenty of other globe projections, as I'm sure you know. Some are best for more accurate distance, some for more accurate depiction of area, and some for the intuitive representation of direction.
What if the 3D object to unwrap isn't a regular solid? What if it's a cow, or a... human, or an... AIRPLANE!
At the least, each piece needs to be unwrapped separately, and the way the software unwraps it may not give an intuitive result, because there are
so many unique ways that a 3D object can be covered by a 2D surface.
I'm typing this out for my own understanding as well as anybody else's. If you more-experienced unwrappers have input, PLEASE give it.

