One problem is that "keeping the crap away from your employees" can become a solid barrier to employees whose desired career direction involves strategic leadership.

Those employees can have a hard time getting involved at higher levels of the company, exactly because their job is so cordoned off from everything. Which leaves people in the cliched position of needing to perform well enough Job A to get promoted out of it. (Which has always been a logical flaw in the corporate world.)

There certainly are other solutions to this problem -- this is just one solution, and is probably also targeted as a solution for other issues as well.