Babel Loader Version:
current (8.0.0-beta.0) but I believe it stays since beginning (or at least 6.x)

Current behavior:
When cacheDirectory option is set, babel-loader stores the cached transforms as compressed files (using zlib).

Expected/desired behavior:
I'm actually curious what's the idea behind compressing cache?

The only reason I can see is to make node_modules take less place (as node_modules/.cache/babel-loader is the default cache dir)

The drawback, however, is spending quite some time compressing and decompressing (not to mention stringifying and parsing prior to that).

Would you be interested in accepting a PR that at least would make compression customisable?