Red Bull decided not to choose Carlos this year, rather than the other way around, this is the second time they decided against making him Max's teammate. I think the number of people who believe Carlos would do the same or worse than Checo is one: Checo's dad. Not even Checo would believe that right now.

Why would they not sign him? I doubt he held out for salary parity to Max, the most I would expect is a number 2 contract as Massa or Barrichello are rumored to have had when at Ferrari. Williams hardly has the big money to pay drivers...

We aren't comparing that second driver to Max, we are comparing them to Checo, can they score significantly more points than Checo? Even when Red Bull didn't go in the wrong direction with their car to the point even Max was publicly complaining the car was too hard to drive. The Red Bull was peerless last year and Checo was 290 points behind Max, managed 2 races ahead of Max were they both finished, and four more races one place behind Max.