Starting today, your placement matches will again count towards ratings, for 'tis the Season 3 of Overwatch competitive play. With some changes:

After giving the Skill Rating system a major overhaul in Season 2, we noticed both the Gold and Platinum tiers were significantly overpopulated. This meant that some players were initially achieving inappropriately high skill ratings and then experiencing a downward adjustment within the first few matches of the season. This also meant that competition within the Gold and Platinum tiers could vary widely from match to match.

To address these issues, we’ve made some slight adjustments to the Skill Rating system—and, as a result, skill ratings will be more widely distributed across all tiers for Season 3. Many players will be ranked lower than expected after their Season 3 placement matches; however, this should normalize as the season progresses.

Source: playoverwatch.com