Many colleges use unweighted GPAs. This is because they want to compare apples-to-apples by looking at all students on the usual four-point scale. Weighted GPAs leave colleges looking at an apples-to-oranges situation that is more difficult to compare.
Colleges may still look at what courses students took to find out who took the most challenging courses, even if they do not accept the weighting that often goes along with the grading of these upper-level courses. Colleges may also take each student's core courses and calculate a new GPA that omits unnecessary classes like gym, music and art. Besides GPA, colleges look at other factors, such as extracurricular activities.