See my other comment below, but all the things you're talking about work because English has a phonetic alphabet.
You can break 'be with ye' into 'b', 'y', and 'e', and drop the rest. In languages like Chinese which do not have a phonetic writing system, you cannot drop individual sounds within a word/character in a rule-based way like contractions.
Emojis are not a phonetic system, so unless you created an emoji for "they're", separate from the emojis for "they" and "are", you wouldn't have it as a word.
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Plenty of words are contractions or otherwise combinations of other words that you don't know about unless you're particularly interested in language.
"Goodbye" = "God be with ye" for example
You don't think "will not" when you say "won't", "won't" is just a word you use with a meaning you understand long before you can write.
See my other comment below, but all the things you're talking about work because English has a phonetic alphabet.
You can break 'be with ye' into 'b', 'y', and 'e', and drop the rest. In languages like Chinese which do not have a phonetic writing system, you cannot drop individual sounds within a word/character in a rule-based way like contractions.
Emojis are not a phonetic system, so unless you created an emoji for "they're", separate from the emojis for "they" and "are", you wouldn't have it as a word.