As a scientist, I think it is important to contribute to the community. One of the ways I have been doing this the last couple years is by reviewing a fair share of papers (currently 44 reviews for 20 different journals). Even if I am busy I try to accept review invitations if I think I can give a proper assessment of the paper.
I have recently decided to join Publons to have an actual official log of my reviewing activity. After adding my whole backlog of reviews it is now as simple as a simple as forwarding an email to Publons to keep track of my reviews. I think it is great scientists get credit or their reviewing and editorial contributions and think that potentially a website like Publons may help provide further incentive for academics to keep fulfilling this important job.