I guess it kinda depends on what you mean by "cultural weight". Alphabet characters just make words, periods et al are just punctuation.

@ is somewhat different. It's not punctuation. It's not a letter. It's a symbol, used primarily as an abbreviation, like %. But while % is universal, @ is more regional.

Sure, these days it's part of email addresses. But it has a long history of meaning others things. And it's been used in different ways in different places and times. Growing up in the 80s, it was on my keyboard, but I had no idea what it was for.

If one takes "culture" here to span time, rather than location, then perhaps the argument makes more sense.