I guess the point it to balance points that is given out.

take a look at this: http://eu.wowarmory.com/arena-calculator.xml

Try with 2200 rating and you realise that in 2v2 you get 300 less points.

Anyway the problem atm is that there are way to few teams doing 5v5 and it makes it hard to climb, but more teams is closing in on 1500 wich should make it pretty easy to hit 1700-1800 if you play at the right time.