Today, URIs don't provide much support for internationalization. With a few (poorly defined) exceptions, today's URIs are comprised of a subset of US-ASCII characters. There are efforts underway that might let us include a richer set of characters in the hostnames and paths of URLs, but right now, these standards have not been widely accepted or deployed. Let's review today's practice.
The URI designers wanted everyone around the world to be able to share URIs with each other—by email, by phone, by billboard, even over the radio. And they wanted URIs to be easy to use and remember. These two goals are in conflict.
To make it easy for folks around the globe to enter, manipulate, and share URIs, the designers chose a very limited set of common characters for URIs (basic Latin alphabet letters, digits, and a few special characters). This small repertoire of characters is supported by most software and keyboards around the world.
Unfortunately, by restricting the character set, the URI designers made it much harder for people around the globe to create URIs that are easy to use and remember. The majority of world citizens don't even recognize the Latin alphabet, making it nearly impossible to remember URIs as abstract patterns.
The URI authors felt it was more important to ensure transcribability and sharability of resource identifiers than to have them consist of the most meaningful characters. So we have URIs ...