Yes, what Velbert said. Also, having attendants in the cage with the queen, they can be possessive and fight with the bees in the hive and the queen can be damaged. The bees in the hive are queenless and they know it and want the queen, they don't want any strange bees along with her. Also, sometimes what the attendants might be are older bees caught to be put in the cage with her to care for her, instead of younger nurse bees maybe?
I purchased a couple breeder queens from Glenn Apiaries and they recommend removing attendants and introducing the queen in a pushin cage.
A pollinator who I worked his hives with for a year also stated that he had more problems with queen introduction if he left the attendants in the queen cage. He always removes them, and I do likewise now.
I've been keeping a few hives for the past 20-25 years, and no longer treatment free as I got tired of the losses.