What Las Palomas probably realized is that they're going to incur on site costs (security, common area maintenance, etc) from all renters. Now when somebody uses another agency, or pockets all expenses, how does that get paid for?
Also, Dry Heat mentioned that Las Palomas is the highest ranked property on Tripadvisor. This is probably because they're able to offer guest assistance on site, have a consistent product for renters, etc... What many guests may not understand is if you rent a unit through Oceano, at say Bella Sirena, and then something goes wrong, they can't just go to the front desk and get it taken care of. To their amazement, they need to either place a call (do they have cell service?), or trek across town to tell somebody at the office over by Las Conchas. Of course the problem probably isn't addressed until their vacation is over. And there you have it, 2* tripadvisor review.