1. The other UUID versions are actually used. However, the expectations is in what the developer gets when generating it. Even "random ID" can be messed up if the author tries to be smart - e.g., rolling their own secret chronical sortability hack for their database but not telling you how much entropy and collision resistance you have left, or them hacking in multi-server collision resistance by making some bits a static server ID.
People have reason to do those things, and oh boy do you want to know that it's happening. With UUID, over-engineered as it may be, you know what you're asking for and can see what you're getting - truly random, server namespaced, or chronologically sortable.
2. Being upset over 4 bytes wasted to hyphens but not being upset about JSON itself seems hypocritical. JSON is extremely wasteful on the wire, and if you switch to something more efficient you also get to just send the UUID as 16 bytes. That's a lot more than 4 bytes saved.
Over JSON you can still base64 encode the UUID if it's not meant to be user-facing.
People have reason to do those things, and oh boy do you want to know that it's happening. With UUID, over-engineered as it may be, you know what you're asking for and can see what you're getting - truly random, server namespaced, or chronologically sortable.
2. Being upset over 4 bytes wasted to hyphens but not being upset about JSON itself seems hypocritical. JSON is extremely wasteful on the wire, and if you switch to something more efficient you also get to just send the UUID as 16 bytes. That's a lot more than 4 bytes saved.
Over JSON you can still base64 encode the UUID if it's not meant to be user-facing.