Sometimes, yes, people who are offered things understand precisely what's going on.

Take, for example, someone who reads popular science magazines who is offered an experimental therapy. That person, while not a medical professional, is more likely to understand than, say, someone with a high school diploma from a school without a good science department who doesn't read popular culture magazines that deal with science. The latter is more likely to trust the professional suggesting the therapy.

People who apply for mortgages without much knowledge of financial matters -- and American schools are very bad at requiring financial competence as part of their requirements for graduation -- are more likely to trust the professionals suggesting a particular mortgage. As we all know (now), many of these mortagages were thought of by the organizations offering them as something to sell to someone else. The needs of the applicants, in such cases, may not have been high on the list of the banks and brokers, who would have shed themselves of the mortgages. Ability of applicants to pay becomes the holder's problem, rather than the way it was in the olden days when a bank held the mortgage until it was paid off, and thus retained an interest beyond doing the right thing in making sure an applicant was able to repay.

Add an inability to ask the right questions because of ignorance, willful or otherwise, and you have applicants who signed something they didn't understand because they trusted the professionals.

The difference? The medical professional took an oath to look out for the patient, which is enforced, sometimes not too well, but enforced nonetheless by the profession. The financial professional is guided only by personal ethics and by government regulations. Absent the regulations, you better either know as much about mortgages as the people offering them, or hope you got an ethical broker.