It's not that they are putting all titles on RAW, but the Brand split is as good as over and now, we have many titles and champions appear on both shows regardless of which brand has the title.
You can't also forget the fact that Raw Supershow is supposed to include superstars from both RAW & SmackDown, and it's a 3 hours show that has to be filled, so it's only natural that the show will include more champions anyway.