I'd have said that they were not felted enough - the original 'cappers' used to felt, brush, clip and generally work quite hard to make the knitted look dissappear entirely.

Although on some of the museum items which were knitted the stitches are visible, I suspect that they are simply threadbare and the original raised nap has worn off.

I have knitted and crocheted caps and hats almost as long as I have been making socks, and to make a good solid felted hat is no easy matter - whilst the shapes and even the colours of those on offer might be right, I suspect the weight and rigidity would be wrong.