"Targeted" exercises tend to be body-builder type stuff which can only really be done with light weights. Instead, bigger compound movements like squat and deadlift can be incrementally trained leading up to much, much heavier weights and they train the body as an integrated whole.

In daily life, the body is used to move with many muscle groups working together. By using a targeted exercise, you can create muscle imbalances and injury is more likely (especially stuff like tendonitis).