JDK is right:
Because if you raise in a loose game, you're more likely to get called by hands worse than your own. If you raise in a tight game, the calls will be hands that are more likely to have you dominated.

You want to avoid the potential for being dominated. When you hit, you will win small pots, lose big ones and fold winning hands in a tight game. In a loose game you will find it harder to drive out several opponents with top pair from early position. As a result, you want to narrow the field preflop.

Is this no-limit or limit