Here's why:
* Dragon hide is very difficult to obtain: Dragons are incredibly powerful and dangerous creatures, and obtaining their hide would be an extremely risky and likely illegal undertaking.
* Dragon hide is valuable: It is often used for magical items, such as dragon scale shields, so it would be highly unlikely to be used for something as mundane as gloves.
* There are other magical gloves: While dragon hide gloves don't exist, there are other magical gloves in the Harry Potter world, such as the gloves worn by the Dementors.
It's possible that the concept of dragon hide gloves is a fan-made creation. If you're looking for information on specific magical items in Harry Potter, it's best to refer to the official books and movies.