Why does IntelliJ keep removing backticks from this JavaScript template string?

I have the same problem. I solved it by disabling the "Insert pair quote" option in Preferences -> Editor -> General -> Smart Keys.

Of course, it disables the inserting of pair quotes for all types of quotes, including single and double. It's a temporary workaround, but personally I'd rather actually be able to use JS's template strings despite having to type in the pair of quotes every time.