Why do you think Friar Laurence doesn’t reveal Juliet’s prior marriage to either Paris or Lord Capulet?

Answer 1

Quite simply, I think he's afraid of their wrath. That's why he wants to let Romeo and Juliet disappear together. If their families found out they secretly got married, there's no telling what they might do. For one thing, they could get the marriage annulled and force them to marry other people - and that would actually be the best outcome.

Since only the two themselves and Friar Lawrence knew about the marriage, they could also just have killed him and pretended it never happened. Remember, both families are quite ruthless in protecting their interests. They might even have killed R&J themselves, because they felt the two dishonored their families.

In a nutshell, he doesn't tell them because it'd be much to dangerous, and he'd rather get the two of them away to safety before anyone catches on to what happened.

Answer 2

the wording on that is a little off but I think I know what you meant. I think that the friar knew that Romeo and Juliet were going to be together in any case and being a friar, believed they were better off at least married. He also must have agreed with them that it was best for the family not to know.

Simple answer- he's a priest. He was under a vow. He COULDNT tell them. All he could do was try to help and guide the couple. It would be against his vows to tell anyone else anything.