What's up with "Could"?

I suppose the title of this post doesn't convey my question very well.

What I'm wondering about is why I see so many narratives where we are told that some "could see" or "could hear" something. For example:

She could see the ducks in the pond.

Or

He could hear the rumble of trucks on the nearby freeway.

Why "could"? (Which is one of those words that starts looking odd after you've written it too many times...)

In the case of the first example, the author might have instead written

She saw the ducks in the pond.

Or even, if we are clearly embedded in her POV,

The ducks paddled across the pond. (etc)

Why the "could see" construction? When I read it too many times, I find myself asking, "She could see? But what? She could, but chose not to? She could see, but instead put her hands over her eyes?"

Now, there are completely legitimate uses of this construction, especially when it follows a change in conditions:

Standing on the box, he could see over the fence

Or

Once he turned off the car's engine, he could hear the chirping of the crickets in the field.

But the longer I think about it, the less I like

He could hear the chirping of the crickets in the field.

all on its own. Obviously the writer is telling us that he heard them, not that he could have but overlooked them, or the writer would have said something like

Were he not so distracted by his mobile phone, he could have heard the chirping of the crickets in the field.

So why are some writers so tempted to avoid saying

He heard the chirping of the crickets in the field. ?

It has an air of the hypothetical case about it. Are people drawn to the "could" construction because it's a little weasely? My dictionary notes that could is sometimes used as "an alternative to can suggesting less force or certainty or as a polite form in the present ". In other words, yes, weasely (which in my opinion usually weakens fiction).

Or perhaps it simply has a fine, slightly archaic ring to it (as it were)? I was at a graduation ceremony not too long ago where I heard the slightly formal hypothetical used in an unending stream. As each graduate was announced, we heard something like

John Richard Smith...John would like to thank his parents, and Mrs. Jones at the school library.

Uh-huh. He would like to, but he can't? He'd like to, but is having us do it instead? I, well, could think of reasons he would like to but won't, and after I hear a speaker repeat 'would like to thank' a dozen times, I not only could think of reasons, but I actually do think of reasons. He'd like to, but at the moment he's too stoned to talk. He'd like to, but unfortunately they never helped him, and in fact were the major impediment to his success. He'd like to, but he was captured by Moorish pirates and had his tongue cut out.

(Hey, it helps pass the time. If there's any thing more boring than a graduation ceremony, I never want to attend it.)

I note that could and would are both similar, very old words. And when I think about it, should is pretty fuzzy, too. It must be those -ould words--shifty and circumlocutive.

Of course, I exclude from this category -ould words like mould, which is a very different matter. But perhaps that's why on this side of the Atlantic we spell it mold. I could believe that. I would like to believe that.

I should be ending this post now.