From the clips I saw I have a 質問 about the parents.

Well, maybe some people thought that it wouldn't be very important to give the parents much dialogue in the movie. As they don't have a large role in the story, other than at the beginning, when we're told why Rapunzel is stuck in a tower, and when Rapunzel realises she's the princess and returns to the kingdom. Giving a dialogue for the parents may not have helped the story along to make it entertaining and keep the audience's attention for one and a half hours.

This is just a guess of course. あなた can only ask the producers of the movie. :)