MBAs were often used to give people with other expertise the tools needed to talk to senior leaders using (mostly) financial tools. Their underlying expertise was still a very necessary component of their management jobs.
If you replace that with someone who only has business experience, and no other subject matter expertise, then you have a hollow manager that does not offer real value to the company.
For instance, if a company makes metal boxes, someone who worked in tooling, fabrication, or engineering would be a better MBA candidate than someone who has a business degree and no real experience making metal boxes. They are not going to understand the 'why' behind various decisions that impact production.