You might be confusing regional bus with long distance bus travel or ride for hire bus companies which will also be impacted.
The bus companies which operate official lines for Verkehrsverbünde will get paid the same as always, they’re not affected by the 9-Euro-Ticket.
However, I fail to see how that business, which usually involves a time constraint and direct point-to-point travels, would be impacted by this kind of ticket.