Because they have less activity going on. They have been referred to officially as quiet pools in some references and on some maps but sometimes people have mistaken that for the need/direction to be quiet there which has never been the intent from my understanding.
It's interesting that the text in the image you posted talks about "a serene swim". It gives the impression that Disney did intend for the quiet pools to be quiet. We've usually found that to be the case. DH and I have used the quiet pools when we wanted a break from the noise and crowds in the main pool area. We've generally found only adults there, swimming, relaxing and reading. I think it's nice that those seeking a quiet place to swim have a place to go.
What lifeguards can do is curtail unruly behavior so it's not one guest against another. It's no different than the issues with W/D where conflict is reported not that infrequently. As a group the current generations simply do not have the ethics of previous generations. The general in charge of the Army reserve recently stated this and that they had to teach recruits such ethics that many of us would assume as natural. We see it here, a recent example was someone who said they were going to sneak someone into the room without adding them but yet in the same paragraph stated they wouldn't do anything dishonest.
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We could get into a whole societal discussion on the impact of family and ethics/behavior etc but I have gone off topic far enough 
I think there has been a clear erosion over time and I feel a more rigid approach to areas of rules, laws, ethics and principle are the way to go. More specifically I don't feel the individual has the right to bend or break them unilaterally unless it's a matter of true principle unto itself and are willing to suffer the consequences to make the point. For other areas more flexibility can be reasonable though I'm a "if you're not 5 min early you're late" type of person. That's different than someone trying to impose their own rules which would be applicable if someone got upset that it was not quiet at the "quiet pool" because from what I can tell, Disney never intended for them to be quiet, only acknowledged they were not as exciting and therefore have mislabeled them at times.Agree Dean on Lifeguards helping with unruly behavior. Instead of ethics, we can point to many ethical issues that hit every generation, I will say appropriate behavior, common courtesy, as well as civility is lacking. That conversation can take on a website by itself. Of course the Parents of the 60's probably said the same thing about the younger generation. At the sametime I think the older generations sometimes forget to be flexible or to just enjoy. We become more rigid and more black and white as we age. If I tell my in-laws we are leaving for dinner at 6:30 and my wife is not ready at 6:29 they are frantic. While on vacation it is OK to slow it down, relax, and if someone's behavior is not impacting you, to let it go. In life or on these boards we all sometimes get a little too righteous (not saying you are), people are posting that they would slam shut the pool gates at the Poly and not let someone in if they think they may not be staying at the resort (mind you the person behind them might be a guest there). There are others who are going to write to member Services if kids are throwing a ball or splashing in the pool. Appropriate behavior, common courtesy and civility can be issues at both ends of the generations. I feel very fortunate to be able to say that I see my kids, now young adults, as ones who are polite, are courteous towards others and have high standards of ethics (probably from their Mom
I hope to see you on your raft. I promise I wont splash...much. Enjoy your trip
