The trust aspect is, for many, part of the appeal. You're both vulnerable, emotionally and physically, and giving and getting access to the most private parts of someone else.
Most children have a 'why would someone do that?!?' reaction to discovering some aspects of adult sexuality, and some adults have the same reaction to what some others enjoy.
If it's not for you, it's not for you, but if you can enjoy imagining doing stuff with a fictional person, you can very probably find someone you can enjoy doing stuff with in reality.