There could be several benefits to the learner.
Reflexivity: As this produces a record of their thoughts and experiences throughout the learning experiences. It creates an easy and accessible method of looking back and reflecting on your work.
Aids when asking for help: Similar to the above, but if a record is their from the learner that an educator can read. They then have a way of reviewing the learners work at a glance and pointing them in the right direction more easily than trying to draw information from them. This would make vulnerable interactions where the power imbalance is most apparent to a learner arguably more plateable.
Interactions with peers and colleagues: The blog presents the thoughts of the learner to their colleagues and peers who can then comment and engage with the material posted to create a collective learning experience on the required material. Potentially helping several learners at once.
There are undoubtedly more but these are the main three that spring to mind.