I disagree with the implied notion here that Internet art is any more ephemeral than physical art. Physical art, whether it be a statue or a painting, will eventually need to be preserved and maintained to ensure it is available for future generations. Transferring a digital art file to a different media or changing the storage protocol or making backups in case of data loss is just another form of art preservation.

The key difference being I guess that preserving digital art usually involves making copies and backups as opposed to there being a single-source-of-truth so to speak like the physical world. I think this is the major factor contributing to a lack of digital art in modern collections, it's just too easy to copy.