It is important to know this aspect of STDs because many people find it very arousing to engage in non-penetrative sexual activities. The need and satisfaction requirements of people in sex varies from individual to individual. This leads to exploring newer and non-traditional ways of getting orgasm.
Sometimes hygiene is ignored when there is no penetration. It is wrongly believed that only intercourse has a risk of hygiene.
However, with the knowledge of the STDs mentioned above one can be aware of the risks and take care.