I wonder if parents do secretly hope for good speech skills because they, as hearing people, know how some hearing people view deaf people in general. They have seen how some (if not most!) hearing people feel sorry for them, especially if they don't speak at all. Even after the parents have learned about the benefits of ASL, I wonder if they think to themselves, "Well, that's great and all, but the idea of my child having to deal with the real world without good speech skills is just depressing because I know how cruel hearing people can be." ASL-users making statements about themselves and how they went far in life and how they learned English and so on falls on deaf ears (har har) because the parents believe that it's easy for an ASL-user to not realize how hearing people really perceive them nor treat them due to the communication barrier, especially if the ASL-user get most of their REAL interactions with only the Deaf community. In other words, "They just don't know better."
I often try to see the world through another person's eyes to see if it explains their actions.
A smart hearing person obviously would never admit to wanting good speech skills because they know it technically has nothing to do with being successful. Sort of like a parent wishing that he had a son because a man "can be" more successful in life than a woman.