Spellings change.It was hyphen worthy back in those days of our straw and mud huts and we could have easily confused "email" with a different word altogether that wasnt related to mail or communication. But now we know what it is, with a couple generations not having needed that distinction because they've always had email, and it's common enough that those of us who aren't digital natives easily recognize it. Ergo no more e-mail.
Some day "enuf" & "thru" will be standard, eh.