Square and rectangular frames are better for people with round faces. They balance out the shape of the face and give it a more neutral look. Round frames on round faces make it look too circular.
More rectangular shapes are trendy right now, especially in oversized sunglasses. They are also available in more masculine styles that replicate the look of secret agents or military personnel.
Overall, most rectangular glasses have a very classic, sleek style and they are made by manufacturers from all over because of the simplicity and class.