I’ve recently gone back darker (not to my natural hair colour but similar) from dying my hair blonde for about a year and a half. I’ve both box dyed it and had it bleached/toned professionally. I’ve never come across after a professional appointment where someone who’s “genuinely happy” with the result after bleaching, says that they’ll use tons of purple shampoo to get the brassy tones out. I can definitely see after box dying your hair blonde (especially going from a darker shade) why you’d use a lot of purple shampoo, but most professional hairdressers don’t just leave streaks of orange and yellow in your hair after bleaching it and it isn’t necessary to use purple shampoo on bleached hair beyond maintenance of the colour between washes, not to fix the tone of your hair, that’s what toner is for 
