Even if cross-platform support for a media format sucks, maybe some of us would actually leave the decision on whether the content's crap or not after actually seeing it? And maybe some of us would rather not dual-boot just to use some unsupported media crap.
Adobe is not the only one who should be blamed for this, web designers who forget linux and bsd users are as guilty for adopting media formats not working properly or at all in non-windows/os x operating systems. Another good example is use of Windows Media formats, the formats cannot be decoded on linux and bsd without use of hacky and illegal w32codecs package which is not due to illegality found in supported distro repositories.