David's health scam is true because the elderly lack access to information. Because the elderly lack access to information, they can't keep up with the update and change of information. The so-called well-known health experts in the lecture promote health care products in the process of imparting health knowledge, but also fabricate facts and exaggerate their efficacy. Taking advantage of the general love of the elderly, some unscrupulous businesses also take advantage of the general love of the elderly. For example, getting eggs and traveling for free has almost become the main way for the elderly to participate in the marketing of health care products.