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.
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.
Westerners use it to signify they're pissed while it actually means triumph in Asia I believe.