I guess the first reason would be that all modern browsers have Flash pre-installed, while that isn't the case with Quicktime. Granted, if iTunes installed, Quicktime comes with it, but I've run into cases where more locked-down corporate environments don't allow Quicktime to be installed at all.
A similar question was asked recently on this forum, and I think the responses should be helpful to you - but feel free to ask about anything else:
http://geeksandgod.com/forums/dynamic-website-foru...
Alan.
When I have a flash player to show a video the video doesn't start downloading until I press play. With a quicktime video it starts downloading with the page. That's a big bandwidth difference if people will view a page without pressing play. Like, if they can comment on the video.
Anther reason is the look of the player. Quicktime is quicktime. I can theme a flash player to look good in my site.
There are a lot of reasons....
Recently at the Daytona Beach conference someone brought up the suggestion to put video on the web using flv/swf format over quicktime. I didn't write down the reasons as I am needing to understand and sell the idea to a client. Thanks!