Because
Elizabeth is the English form of
Elisheva, and
Elisheva is a Hebrew name which appears in the Torah / Old Testament. This Israeli popularity list from 2016 is the same as the one here on BtN, except it lists the Hebrew transcription first, and the English translation second.
https://bloodandfrogs.com/2018/04/101-most-popular-jewish-girls-names-in-israel-in-2016.html . Apparently people may use one or the other or both, depending on circumstances.
Elisheva/Elizabeth was #58, which isn't extraordinarily popular. My guess is that it is seen as a true Hebrew name from the Torah which just happens to have an English equivalent, like
Rivka or
Dvora. Its long history of usage in the English-speaking world and elsewhere also means that many people will have ancestors with this name. I don't think you need to seek far and wide for more reasons for its use.
This message was edited 3/18/2019, 10:32 AM