The code in question was added in:
  commit 48ea88c8
  Author: Rüdiger Timm <rt@openoffice.org>
  Date:   Wed Mar 12 09:02:20 2008 +0000
  INTEGRATION: CWS impresstables2 (1.1.2); FILE ADDED

So hard to tell what its original purpose was. Probably trying to clean
up the model, but had the unintended side effect of removing styles.

Change-Id: I7d774706c22cf72e914b356df9bbc5947ee2c1a5
Reviewed-on: https://gerrit.libreoffice.org/28950Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>