The sun doesn’t lose its beauty when covered by clouds, the same way your beauty doesn’t fade out when covered by hijab.
Wearing hijab is a personal and independent decision that comes from a sincere yearning to please ALLAH while appreciating the wisdom underlying this command.
Modest clothing is an integral aspect of worship in Islam as well. The essence of Islam is Submission to the Will of ALLAH. Therefore, if one asks why hijab is necessary, the only proper reply would be “Because ALLAH and his Messenger have so decided”.
In Quran ALLAH says “And say to the believing women that they should lower their gaze and guard their modesty, that should not display their beauty and ornaments except what appear thereof; that they should draw their veils over their bosoms”.
When ALLAH revealed this verse, the female companions of the Prophet (S.A.W) promptly adopted these guidelines. In similar spirit of obedience, Muslim women have maintained modest covering (hijab) ever since.
Hence, the primary motivation for wearing the hijab is to obey ALLAH and Modesty is the part of Iman.