All Flash sites can have alternate HTML content for disabled visitors and/or crippled browsers, via swfObject.
There's not a bit of difference between the Flash alternate HTML content and a plain vanilla standards compliant HTML website.
For example, underneath this
Disney Flash website, there is a simple but functional HTML site.
You could even use PHP to parse the xml or rss data source for the Flash site into a basic functional HTML page in the alternate content div.
Unfortunately, few Flash developers take full advantage of this feature, unless specifically asked (and paid) to do so by their clients.
BTW, the title for this thread is essentially just an observation by the OP; it is not necessarily based on fact.