Priests gather in catacombs, wisper words of faith to small secluded Groups and are hidden by their friends at the hidden cults.
Mages on the other hand stand on high ground, preferably on the balcony of an imposing tower, raise their wizards staffs and shout arcane words that travel far in the storm just conjured.
If they just sit in the library and study everyone knows it as well. Libraries are open to the public and besides the mages constantly complain that the book they want to study is already taken by that old bookworm Theostratus. A clever assassin should have no problem finding Theostratus. Especially as he brings a huge trunk of books with him home each night. Mages are not bright enough to hide from mundane threats.
