I'm a fan of detachable magazines for several reasons, but I also like internal magazines on certain types of rifles for different reasons. To me, it is a choice that is preferable for convenience, for certain types of hunting and the locations that I hunt.
If I'm moose hunting up north, driving down logging roads or hunting from spot to spot on my atv, then, a quick slap of the magazine into the rifle, and your ready for action....or if I'm constantly loading and unloading twice a day, then its faster and easier than loading one bullet at a time.
If I was dangerous game hunting, the internal magazine is a must, for safety, because the risk of recoil causing your magazine to pop out is a factor.