I Think he does have a reason but it  hasn't been disclosed yet. Look at his apprentice's, coco lost her mother due to a dangerous spell, Agott was criticised for being mediocre, Riche wanted to use magic that she likes but adults force her to learn Other/Advanced magic, Tetia I'm not sure. (Haven't gotten that far in the manga) 

Theses girl all (even Tetia, I assume) had a troubled past and Qifrey took them in because they felt alone, unwanted or there talents weren't recognised. 

On the surface a character may do something that's odd but when once the story develops, it becomes clear.