A lot of people seem to play 5's, or even queue but don't enter.
Just for the points, because you get full points in 5's.
In 3's, you get 60% of the points that you would get if you had the same rating in 5's.
Same deal for 2's, except its 40%.

Then they turn around and offer gold to join a 3's team with 2 very geared people.
And be carried up to whatever rating.
Where they already have a bunch of points from their losing 5's.