This is why the landlords care: http://www.your-story.org/new-legislation-for-multiple-occupancy-homes-could-lead-to-rent-rises-warns-manor-lettings-158986/

And of course, rather than the regulations ACTUALLY making life safer for people in shared housing, it just means that the only people willing to rent to sharers are the dumb and the unscrupulous. Grr.