Even after three years, WordPress can't mandate the upgrade because of hosts who won't do the same. "Developer convenience is secondary to the convenience of users": that's why developers tend not to hang around for very long. It's easier to swallow as an employee than as a hobbyist/volunteer.
skeltoac says it's fine to use with other blog platforms, and for all the talk about "hard-core hackers" it's not at all difficult. The reliance on hated XML-RPC keeps me away, but eh.