What limitation prevented Progressive Downloading from being true streaming?

Lack of interactive control over the data stream, making seeking clunky.

Progressive downloading, while an improvement over pure download-then-play methods, still operated fundamentally on the mechanisms of the Hypertext Transfer Protocol (HTTP). HTTP is optimized for requesting a complete file or segment in a single transaction, described as a one-shot action. The key failing for continuous media delivery was its deficiency in providing robust, real-time session control. Operations like pausing playback, or dragging the slider to seek forward or backward, often resulted in the server simply halting data transmission or requiring the client to request an entirely new segment, leading to interruptions and a clunky user experience that lacked the smooth, interactive responsiveness expected of modern streaming. True streaming requires a protocol layer dedicated to managing these ongoing session commands separately from the data transfer itself.