3blue1brown’s video on holography is one of the coolest math videos I’ve ever seen. Basically magic.
Though that also is part of the reason that a they're not more common. Each hologram is the film rather than a "print".
If someone wants to make 100 holograms to be able to sell them as more than a one off art piece you're making 100 units of the film.
Film sheets might be doable.
https://www.geola.com/product/pfg-01-film/ for a Lithuanian distributor. 35cm (about 1 foot) isn't that large. Might be able to cut it into 4ths (classic 4"x5") ... 2"x3" is a small size (12 per sheet).
A hologram is much like a window, you can look through a big window or a small window, and see what's at the other side both times, but the big window still gives you a lot more viewing angles than the small one. Cutting a hologram in half gives you half a hologram, not two copies of the hologram, it's just that you can change your viewing angle to still see what's on the other side, but that will be a different image than with the full hologram.
You get pretty much what you would naively expect from chopping up a hologram before reading that kind of misleading "two copies" text: exactly the same view of the object as you had from that part of the hologram before you cut it up.
It shows a hologram that has been cut into 3 pieces and the aspect of the viewpoint changing as you look through it, though each one has the full subject that was imaged.
My point is that while you can see the full subject you get it from the exact same point of view as that part of the hologram before it was chopped up.
If you couldn't see part of the subject from part of the intact plate you won't be able to after either.
The phrasing you used, "two copies of the hologram" is very misleading in the same way that my Usborne book was.
Chopping a hologram in half gives you two copies of the hologram in exactly the same sense that chopping a photo in half gives you two copies of the photo.
In both cases what you can see from that part of the plate/print is the same before and after you chop it up.
This might be true for current processes but it seems like it should be possible to duplicate a hologram - use a hologram as a stand-in for the original scene when creating a new hologram. The result might have some blur (that progressively gets worse the more 'generations' you are from the original) but that seems like a solvable problem if someone worked at it.
I think the real reason we don't see them is more practical - it's amazing tech but a bit too much of a novelty in its current state, it's just not something that most people would want to put on their wall.