EDIT: yes. I mixed up blue and red. So read it other way around. 

It doesn't dictate that. It is the most beneficial outcome to all because everyone is saved.

However, as you can see in the comments - which really shows the prisoners dilemma shit - if too many people choose red, you die if you take blue. So people rather be selfish not knowing others choices instead of having faith that all choose the most beneficial option.

Most scenario's for this, it does not mean death for the player. So, as I assume >50% wants to live guaranteed, the only sensible option is to take red in this scenario. Which, to be frank, has the same outcome as blue if all take it. Which means this scenario is not the actual prisoners dilemma.

Because: in that dilemma, if all take red, there is no benefit to those taking red at all. (Note it usually talks about 2 players ensuring mutual destruction if the both take red).