Vinyl was physical. As were cassettes, envelopes, postcards etc.

Email has one thing going for it that other platforms similarly didn't offer : It's the first personalised, and therefore recognisable, addressing system for an intangible communications platform that's still largely open (Ex: Unlike twitter et al. which has severely limited means of communication and, more importantly, what I can communicate).

I submit that we don't have an equivalent that's evenly matched and so no basis yet to compare it to. That's not to say there won't be one in the future, but I don't see anything close to matching it today or on the horizon.