awful, awful idea to go for two every time
These are not independent trials. The effect of going for two cannot be viewed in isolation. It directly changes the way the rest of the game is played.
missing does not cost just 1 point. There are hidden points lost later based on game situations. A team might have to later go for two to make up for a missed one earlier. It might become advantageous for an opponent to later go for two, and, if they make it, the missed opportunity cost 2 points then.
As the previous poster pointed out...making it might cause the opponent to go for two later where they can make it up.
EDIT:
This is an example of what happens