For example, because they or the whole locality have been removed from the game.
Examples:
company.volatile.cm_min_plnt.albuquerque
company.volatile.cm_min_qry.raton
company.volatile.cm_min_str.santa_fe
company.volatile.gal_oil_ref.san_rafael
company.volatile.hms_con_svc.san_rafael
company.volatile.gal_oil_gst.hornbrook
Or the old company depot has been replaced by another of the same company:
OLD and unserved: company.volatile.bit_rd_grg.ukiah <-> NEW and served company.volatile.bit_rd_svc.ukiah are both in my savegame.
In a new profile, these companies are then no longer included.
It would be desirable if a developer could take care of this matter and remove these abandoned entries.