Why is that?
Plastic pipes, clam shell packaging, kid’s toys, etc… used everywhere and very strong and durable. And a good choice for the usage.
But CD jewel cases will crack and break at the first excuse. :mad:
They are a form of technology that has been around for almost forty years and it doesn’t work well at all.
It is made out of polystyrene.
From the 'pedia:
So it’s really cheap. That’s why they use it even though it’s crap.
There are a few hundred thousand “Plastics” out there.
A very famous line from “The Graduate” comes to mind…
That’s always the answer to questions like these. You didn’t even have to know what plastics are.
But I had a cite! 
Technically, plastic is not a material but rather a characteristic of certain materials.
Both are true. A “plastic”, used as a noun, refers to a class of moldable polymers. Other substances which are malleable and can be molded into solid objects are called “plastic”, used as an adjective.
Plastic certainly isn’t “a” material. It can be any one of a very large class of materials, or even a mixture of multiple such materials (ABS, for instance, which Lego and some 3d-printed objects are made from, is a mixture of three different plastics).
See. You didn’t have to know what plastics are.
In other words not simply a mixture but a polymer alloy.
Yeah, tech that’s been around for awhile… Doesn’t mean it’s necessarily the best… It just means that we swallow it.:smack:
Doesn’t it have to have a metal component to be an alloy?
The formal definition of alloy is specifically talking about a mixture of metals.
ABS is somewhat analogous to an alloy.
Wood is a pretty tough material except for those kids’ toy airplanes. Why is that?
Wooden furniture, house framing, kid’s toys, etc… used everywhere and very strong and durable. And a good choice for the usage.
But kids’ toy airplanes will crack and break at the first excuse.
They are a form of technology that has been around for thousands of years and it doesn’t work well at all.
Try sitting in a chair made of balsa wood and you’ll see why those toy airplanes are so fragile. 
Nah, it’s common today for various polymer compounds to be referred to as alloys. Metal or plastic, the concept is essentially the same.
Whoosh.
transparent (clear) plastics like polystyrene and polycarbonate tend to be rigid and more brittle, and more prone to cracking. since the album art/booklet was meant to slide in to the CD case cover, the rigidity clarity of the plastic was more important.
kids toys and the other examples you mentioned are made from different polymers. “knock-around” stuff like big wheel trikes and the like are generally made from polyethylene (PE,) which is flexible and resistant to impacts. but PE is typically not clear, at best it’s translucent (milk jugs.) a PE blend which is transparent (PET) is used for soda bottles, but it’s too flexible/bendy for a CD case cover. ABS and blends like PC-ABS tend to have good impact resistance, but again are almost never transparent. there is ABS out there which is transparent, but guess what? it has much less impact resistance.
(Note: polycarbonate is what the CDs themselves are made out of. Much stronger in this case.)
I was thinking about the history of media packaging. I think audio cassettes were the first to use polystyrene shells. I don’t think people generally kept 8-tracks in individual plastic shells.
The shells of cassettes have an advantage over CD jewel cases in terms of compact size, wider edges, etc. All of which reduce the forces on and strengthen the hinges. (But they still could be broken with little effort.)
I think the experience with cassette shells lead to the adoption of CD jewel cases. Note that CDs were initially often sold in long box packaging. That increased the total cost of packaging so keeping the jewel case part cheap had to be a factor.
(One oddity about the heyday of cassettes vs. CDs was that CDs were much cheaper to produce but carried a premium price.)
Video cassettes eschewed clear cases in favor of cardboard and soft plastic packaging.
Of course the successor to BluRays will have no packaging at all. 
I know the OP didn’t ask, but: after having years of experience mailing CDs I have found a design that withstands the USPS machinery: the clamshell type, such as these (not these in particular, just representative):