I noticed a pattern, which is when a word ending in 'e' is followed by a word beginning in 'e', the trailing 'e' (and space) in the first word is replaced by an apostrophe. For example:
Ce est -> C'est
Le école -> L'école
However, no one does this:
Elle est -> Ell'est
Why?
For that matter, why don't we contract every final e before a vowel?
On the one hand, you're right. The sound is dropped. Elle est is definitely two syllables, similarly to l'école.
On the other hand, the sound is typically not pronounced anyway. Since it's read as though it ends with a consonant, it doesn't feel like we need to mark the contraction. The words that we do that for are the ones where the schwa that gets dropped is the one and only vowel in the word: le, de, ne, me, te, se, que.
That said, there are exceptions and one could argue the opposite case. One point is that in some dialects, that final e does get pronounced, so there's a difference between elle on its own and in elle est. Another is that words like puisque and jusque get contracted even though the e is unstressed and has basically the same weight as that of elle.
At the end of the day, it comes down to the conventions in place when the orthography was standardized.
Replacing the final e by an apostrophe is done only on ONE syllable words like ce, de, je, le, me, ne, que, se, te...
note that the e must be "neutral" = not accent, no é or è or ê and so on...
and the word must be "grammatical" words like pronouns... no name of generic objects, nor a proper noun
The rule works also for nobiliary particle Le chevalier d’Artagnan
So "jusque" seems to be one of the exceptions.
Although you may find "jusques alors" for poetic/phonetic reasons.