Having seen these at several large corporations, I always figured it was either:
1. a division of labor: each corporate "division"—themselves large enough to have their own subsumed IT departments—gets its own hostname prefix to plan a routing map under.
2. a division in time: creating a new wwwN "prefix" allows them to "throw out" their old route-map and start again for new projects, while still keeping old projects on their existing routes at the old hostname.
My guess leans more toward the second option: corporations large enough to maintain extensive intranets have a particularly faithful dedication to the "cool URLs don't change" philosophy, because they don't want to go around fixing thousands of links built into dozens or hundreds of internal apps, emails, calendars, &c.
Of course, if you know you're going to do this from the beginning, you can just do what the W3 recommends, and begin each newly-defined route with a prefix for the current year+month (see https://www.w3.org/2005/07/13-nsuri).
1. a division of labor: each corporate "division"—themselves large enough to have their own subsumed IT departments—gets its own hostname prefix to plan a routing map under.
2. a division in time: creating a new wwwN "prefix" allows them to "throw out" their old route-map and start again for new projects, while still keeping old projects on their existing routes at the old hostname.
My guess leans more toward the second option: corporations large enough to maintain extensive intranets have a particularly faithful dedication to the "cool URLs don't change" philosophy, because they don't want to go around fixing thousands of links built into dozens or hundreds of internal apps, emails, calendars, &c.
Of course, if you know you're going to do this from the beginning, you can just do what the W3 recommends, and begin each newly-defined route with a prefix for the current year+month (see https://www.w3.org/2005/07/13-nsuri).