They're really not though, because they render differently on different devices. If I send a gun emoji, it may render as a squirt gun for you for instance. Very different meanings.
Also the way I feel about certain emojis is different from how you feel about them and thus carry different (if slightly) meaning.
For example, I pretty much never use the clown emoji as I find it personally offensive. But I'm sure that pretty much everyone else doesn't feel the same about it.