Polite enough, but why not say from the beginning how many interview rounds there would be?

After the first interview, they said there would be a second round, and I completed it. After the second round, they suddenly said there would be a third round. Having a junior engineer interview with the general manager is quite absurd. Then, after discussing the salary directly with the general manager, I was even offered a lower salary. In ten years of working, I’ve never seen an interview process like this—slow and bureaucratic.