A big challenge with rigid social expectations is identifying the beneficial ones and removing the harmful ones. In practice, there tends to be little introspection about which traditional expectations help and which ones hurt. Instead, people appeal to tradition itself as evidence that an expectation is helpful. If we could more effectively iterate on these social expectations then we'd be able to more effectively optimize. But efforts to do this (e.g., discussion of topics like "toxic masculinity") are by-and-large rejected out of hand by traditionalists.
Another challenge is that social expectations may help on average but they may completely fail in individual cases. For example, having both parents raise a child will, on average, lead to improved outcomes. But if we codify this as a rigid rule, then people are unable to escape abusive relationships where the presence of both parents is a negative. Social expectations are necessarily generalizations and people need the freedom to identify when they are not helpful for their particular situation and adjust accordingly.