High attrition is a problem faced by most PhD programs - Not only by those in business. Reasons are many and range from bad selection by student/Program to non-interest and lucrative job. Phd is a different beast than an MBA because of two main reasons
(a) The time period is very long
(b) There is almost zero pressure to perform once you enter the dissertation stage, so one has to be highly self-motivated
That said, I am not sure there are malignant programs, hell bent on throwing people out. A PhD takes so much resources of a school that schools will be foolish to do any experiments just for the heck of it. Most PhD programs are tough - you will not find easy PhD, and if you do, its value in Academic community will be low.
However, there are comparatively tougher programs - but this is not generalizable by a school - only by specilaization AND school. The POM area in Rochester - Simon School - is one where less than 50% students make it !. At my school, in the current third year of Phd, there are 10 students remaining out of 12 who entered. However, both the students chucked out were from Marketing area. So .... it depends.