SWF Files grayed out in Safari's file menu

This is weird, but apparently it does it in 4 and 5. I just never had cause to notice. I'm working in Flash on a PC, brought an swf to mac to try it in different browsers. It'll open ok in Firefox. But in the Safari open file menu it's grayed out - in spite of the fact that it loads these from websites all the time without issue. So I went into Get Info for the file and found that neither Safari or Firefox were listed under 'Recommended Apps'. It did list Quicktime, which insisted it was not a movie (it even has Flip 4 Mac and Perian).
I finally got it to load by clicking 'Show ALL applications' and clicking open with Safari.

But why on Earth did I have to go thru all that? Does anyone know why mac doesn't recognize a simple swf file as openable on it's own hard drive?