As a general rule I agree with you, but as with all things in life there is a spectrum to this. How could you be with somebody that you can't trust is definitely an aspect of this worth exploring, but I have seen a person in a relationship with somebody else smash their phone to prevent their partner from accessing it, after a lengthy period of acting suspiciously in their relationship and finally being questioned with "What's going on?" As the mediator of this particular conflict, I felt this was a healthy question because the person asking it was genuinely concerned about their partner and how they felt about the relationship.

You can guess how this relationship ended.​ You should be able to trust your partner, but there are limits to this and sometimes that trust needs to be verified when somebody is legitimately acting sketchy. You don't want to be sinking time and effort into a relationship that's doomed, that's not fair to yourself. But being an authoritarian goon isn't fair to your partner. Trust until you're given reason not to, and if you can't trust your partner and the reason not to is sufficient, leave.