The CASB was wise to listen to feedback from those most affected by the guidance provided in CAS 418. The expertise required for the reciprocal services method is substantial. But perhaps more relevant are the computational resources. With two or three support departments, computing allocations using algebraic functions can be quite challenging. With 20 to 30 support departments, this allocation would be nearly impossible without access to substantial computing power. These resources are readily available today, but were more scarce in the 1970s.
Just because a company can use the more accurate reciprocal services method does not mean it should use this method. Method choice is a subjective judgment that must be made based on the costs and benefits of each option. If the cost of additional cost allocation accuracy outweighs the benefits, a less costly (and less accurate) method should be considered. The direct and sequential methods are still the most commonly used methods.