Given that the original question asks about why it's curved (and not about how to 'reduce the low-resolution segregation-ness' which is now being asked in comments):

The lines aren't actually curved. It's an optical illusion as a result of the data points being around the line, close enough to mess with your perception of the actual state of the line - it's really actually straight.

An example of this is seen in the U&L Meta post on the Community Promotion Ads - this post on the ad list shows how the lines are perceived as curved, when they're really actually straight.

Given that the original question asks about why it's curved (and not about how to 'reduce the low-resolution segregation-ness' which is now being asked in comments):

The lines aren't actually curved. It's an optical illusion as a result of the data points being around the line, close enough to mess with your perception of the actual state of the line - it's really actually straight.

An example of this is seen in the U&L Meta post on the Community Promotion Ads - this post on the ad list shows how the lines are perceived as curved, when they're really actually straight.

Given that the original question asks about why it's curved:

The lines aren't actually curved. It's an optical illusion as a result of the data points being around the line, close enough to mess with your perception of the actual state of the line - it's really actually straight.

Given that the original question asks about why it's curved (and not about how to 'reduce the low-resolution segregation-ness' which is now being asked in comments):

The lines aren't actually curved. It's an optical illusion as a result of the data points being around the line, close enough to mess with your perception of the actual state of the line - it's really actually straight.

An example of this is seen in the U&L Meta post on the Community Promotion Ads - this post on the ad list shows how the lines are perceived as curved, when they're really actually straight.