I absolutely and completely agree. I love playing magic types... Wizards, Sorcerers, Mage, whatever you want to call them, but I'm so very tired of them having to wear a dress. Why can't my wizard wear pants?
Probably along the same lines why Priest's do:
Vestments are a sacramental. That means they are set apart and blessed by the Church to excite good thoughts and to increase devotion in those who see and those who use them. They are the uniform of the priest when he is “on duty,” while he is exercising the functions of his ministry and using the sacred powers which he received at his ordination.
A Wizard in T and Jeans.... they have more class than that of a commoner.