But you can abstract it all away, with the frameworks that generate the HTML for you. Presumably you're going to be spitting out HTML/CSS/Javascript after some back end processing. You are free to create whatever abstraction you wish in order to accomplish this for you.
The problem with using something like Flex is that it's not available on all platforms and it's proprietary. When you develop for open platforms, you can avoid lock-in and have a higher chance of the technology being available to everyone. If HTML/CSS/Javascript can do everything you need (and I admit that in some cases it can't) and you are using something else simply because it has better abstractions, it seems to me that the lack of abstraction is a consequence of laziness or lack of imagination.
