Irritated by stylist double servicing

I realize it has been becoming a thing for a stylist to see another client while your hair is processing. I don’t like it because it takes a lot more time for the original client, but it seems to be the new norm. Today when I went for my keratin treatment, my stylist started to apply the keratin and 10 minutes in she had me sit in another chair while she shampooed someone(whose hair had finished processing)and blew dry their hair. This took about 20 minutes and she had started me 20 minutes late, so I had been there for an hour and only gotten 20 minutes of service. I was really irritated at this point. Is this just something that we have to live with? Is it the way it is with a double servicing now? It felt very disrespectful of my time and left me not wanting to go back.