AJo, Early Position Question

[XxGodJrxX]

I have been thinking about this for a while, and am having trouble reaching a definite conclusion. You have AJo in first position in a tight game. Do you raise or call? I have seen many different charts and websites and such that suggest to call in a tight game and raise in a loose game. Why would this be the most profitable play? In a loose game, there is likely to be three or four people in the pot regardless of whether you raise or not, diminishing your chances of winning the pot. On the other hand, in a tight game, you will likely play the hand heads-up, where a hand like AJo does really well.

I do usually raise in AJo in both tight and loose games, but I just have to wonder why it is BETTER to raise with it in a loose game than in a tight game. Explanations?