Some people are too embarrassed to buy condoms. Many people simply do not want to bother using condoms. The use of condoms may not be acceptable in certain religious and cultural groups. In some cultures, it may not be acceptable for a woman to ask a man to use a condom. Some people say that condoms reduce sensitivity, and the man loses his erection as a result.
Some people are allergic to latex.
Others do not like the smell or feel of latex. As you can see, there are numerous barriers to condom use, and practicing safer sex. Just learning about HIV and other STDs is not enough. Safer sex involves not only education, but behavioral changes as well. All the education in the world will not do any good, if a person does not change their behavior.