I think you are taking the abstraction too far. True, there are some very significant similarities but there are also differences and although they may be subtle, such differences can lead to vastly different uses. Facebook and Twitter were never "officially" about posting short-lived, single-view posts the way Snapchat is and I for one never used them like that (and I've been on both for many years).

You might be right about ads eventually ruining it, but that doesn't mean that it's otherwise identical.