This corresponds to the different roles and social interaction for men and women in Pakistani society, where women are more isolated from other deaf persons than men. In India the difference, as well as the assignment of social roles, is less marked. But they don't necessarily do so. Socialisation and language attitude probably also plays a role in individual variation, e.g. marriage to a hearing vs. a deaf person, greater or lesser influence of oral schooling. The use of mouthing may sometimes be seen as more 'formal' and appropriate, e.g. in an interview situation.
Some text types seem to be more or less likely to be combined with mouthings.
This point has not been considered in detail yet. I interpret the data as indicative of the fact that mouthings are a contact phenomenon resulting from more or less close contact with a spoken language. The more exposure to spoken language, the more mouthings will occur. This results from points 1. to 4. above. Secondly, within the individual range of each signer a choice can be made to use more or less mouthings depending on context.