There is only one caller of ParserBeforeStrip: the translate extension.
However, we will likely have to introduce a new ParserBeforeReplaceVariables hook for use by Translate. See https://gerrit.wikimedia.org/r/#/c/mediawiki/core/+/446984/
That's probably still better than keeping Before/AfterStrip around, since those hooks are misnamed, redundant, and have lingering references in their signatures.