Other reasons or purposed for using the Pimpl Idoim

As the title suggests, I was wondering what other reasons, purposes or uses are there for the PImpl idiom other than reducing rebuild times.

Quoting an example from here:

(thread locals need to be behind a pimpl wall; they can't be exported directly

I don't understand what the user means, but I gather there are other interesting uses for the PImpl idiom,