Refusing to support older technologies helps encourage people to start using the newer technologies. If everyone dropped support for flash (obviously this wouldn't actually happen) then developers would be forced to use alternatives. If flash continues to be supported then developers have less of an incentive to replace their current solutions.
It would be an irresponsible developer that let loose with full HTML5 site aimed at "normal" people any time soon if they didnt provide a full standard HTML version as well, which begs a huge budget question. Unless they have no marketing department or CTO to answer to of course.
If by "newer technologies" you mean "The Apple App Store" then you have a point. If you mean HTML5, then you have been taken to the cleaners are terribly gullible.
However, i'll bite. Why would I be gullible for believing that HTML 5 (and by extention, the APIs such as canvas and offline storage) is newer than Flash? Acording to Wikipedia, the first working draft of HTML 5 was published in 2008. Flash has been around for a lot longer than this.