I think SHRM has been widely accepted both by academics and HR professionals simply because it links HR practices with general business goals and shows how the HR can play an executive role in organizational performance.
There is a lot of business case for SHRM since it improves talent management, employee engagement, and adaptability which are in high demand for competitive advantage. Although this may be self-serving, the advantages of SHRM for organizational success are so strong it would hard to refute.