Well, that's one reason. Let's think about the functions of HRT. It can:
+ Hedge (and make the speaker look less presumptuous)
+ Engage the other speakers
+ Either hold the floor or relinquish it, depending on the information that's preceeded the utterance
+ Create an informal register
I'm sure there are other reasons, but these ones can help to explain why females are likely to use HRT. As you've already mentioned, females have been shown to be very perceptive to social changes, and are often focused on the relationships that are created through spoken interaction, not just the information that's conveyed. This means that female speakers are likely to ensure that other people are listening, and probably don't want to come across as too blunt. There's also the fact that HRT was initially associated with female speakers, and people are more likely to mimic the language used by members of their own demographic.