A retriever that will not go into the water is, no doubt, the product of an owner that will not go into the field with a gun.
Of course we see the same thing in the world of terriers, and we even have the chorus of a song about it:
Now at Cruft's famous show down in London,.
They have Lakelands that aren't worth the name,
If you showed em a fox or an otter
They would fly for their lives without shame.
They're not built to creep or do battle,
But to sit on a chair in the house,
And they do say that one recent champion
Was chased down the road by a mouse!