I believe that lack of habit formation is a big part of at least some ADHD cases. Having your unconscious make something a habit is how you learn to focus, if your unconscious doesn't decide to make things habits and instead just look for new ways and solutions to do stuff you'll have a hard time focusing.

I don't think that lack of habit formation is necessarily a bad thing, making something a habit is good if that something is good, but bad if you learn things that are wrong. Meaning I'd argue that people who are worse at forming habits are likely better at rethinking their beliefs and theories.