I do not think HR professionals have embraced SHRM out of self-interest alone, let me tell you why. While HRM might be mostly focusing on the regular, day-to-day HR tasks like recruitment, training, development, etc etc, these are still considered short-term goals because these alone cannot help in long-term goals like employee retention and might cause the business to lose high-potential employees.
This is where SHRM comes in handy. SHRM emphasizes growth, development, well-being, and advancement. This leads to growing the employees' loyalty to the business and helps in making employees maximize their performance to help the company reach its goals.
Now this is only one point, and there are many others than just employee retention, and they all benefit the business as well as the HR professionals by giving them more recognition and advanced career opportunities. In the end, I think it's a mutual benefit for both HR professionals and the business.