Worse treatment doesn't really mean much unless the hotel is close to 100% capacity. I may have phrased that part badly - what I meant is that 3rd party custom

Worse treatment doesn't really mean much unless the hotel is close to 100% capacity. I may have phrased that part badly - what I meant is that 3rd party customers are lower priority than 1st party, so if it comes down to a question of who gets the nicer room, 3rd party will lose. With respect to ratings, very few people actually leave them. So you're looking at the uncommon case of a traveler being negatively impacted, multiplied by the chance they even notice or care (e.g. someone who sleeps like a log getting the noisy room), multiplied by the chance that they actually bother reviewing. Couple that with the fact that pickier customers (frequent business travelers, points bloggers, or just brand loyalists) are vastly more likely to book direct, since you generally can't use/gain loyalty program points when booking through an aggregator, and it's understandable why direct customers might get preferential treatment. Not to mention that they're making more money from the direct customers to begin with.