It's kind of a stupid reason, but it's tied into his identity. They let him look at things deeper than he normally would. His mentor/the big bad of the series/ the guy who made him what he is and that Kidou is constantly trying to define himself away from gave them to him. He does not feel as useful without them. He can't be what he needs to be, and if he's not, what is he?

tldr long complex identity issues from crappy father figure.