Reasons, many:
Because its the only thing that feels right, down to the core.
Because all logic , all intelligence, all justice has to have a perfect standard which can only be granted by a higher power, and controls the dynamics of this world subtly, yet completely.
Because I have seen evil being punished, and goodness being returned in great amounts, even though when the man made systems have failed to recognize that evil and that goodness.
Because my need to understand this world and the urge to find the truth has only been satisfactorily answered by reading the history of Islam, its predictions coming true, and understanding the current world situation which was only best explained in the hadith literature of Islam.
because its the only thing that makes sense and makes you live to your full potential, kills the dead feeling inside of you, brings love peace and calmness to your heart and your senses.
SubhanALlah (Pure is ALlah swt) there are so many reasons that they cannot be listed...