Hey Raden, this is such a great question.
I guess most iconic and lasting designs have an intrinsic symbolic relevance. They're not iconic because of their shape or function but because they embody an idea, an ethos or their zeitgeist. Software has had their own icons but I guess, like you say, that their ephemeral nature truly reduces their impact in society and their staying power on our collective consciousness.
There are also issues of how to communicate software design. You can put a vase or chair in a pedestal, you can frame a famous movie poster and people will understand them but you can't display a great piece of software design, fundamentally because a lot of what's important in digital is interactivity.