[fmxexpress]

I ran one of the large flash game portals. We had 100,000 Flash games. It matters because of distribution. One distribution mechanism was through MochiMedia and MochiAds. You'd upload an SWF to MochiMedia's site and they would aggregate it out to thousands of other sites. Without a playable package format you would have had millions and millions of files. Game creators liked the "copy protection" that the SWF package provided and game sites liked the "sandboxed" game files. If a browser could host a ZIP file and load all the assets out of it as if it was a sandboxed local directory that would be the equivalent.