Hairdressers please explain: why do you cut too much hair off every-single-time?

No matter the price I pay for a haircut, no matter the prestige of the salon, no matter the seniority of the stylist, no matter the city or the country, no matter what we agree at the beginning of the session, no matter how long it's been since my last trim, no matter how healthy or damaged my ends are, no matter if they're cutting dry or wet or both, no matter if my hair is straight or wavy - I always go to the salon with my hair at my waist or just below my under bust , and I leave the salon with my hair either at my armpit or just above the nipple. I just had a 'trim' and was promised no more than two fingers off the ends. He even complimented me on how strong and healthy my hair was and how I had no slit ends- this was truly a preventative trim to maintain the style and to remove volume. Yet 60 minutes later and my hair is about 6 inches shorter than before. Don't hairdressers realise their clients would visit them way more often if they actually did what they said? Like now I have to wait for my hair to get down to my waist before I can get another trim! Why can't I just maintain the length? What am I missing? Once I had a dramatic cut and removed over 12 inches of length in one go. Guess what happened when I went to another salon for a hair mask and hydrating treatment a few weeks later? They said I was due for a trim! How is it my hair can be super healthy and strong with no split ends and still need 6 inches removed off the lengths? How is it I can remove 12 inches off the length of virgin hair that has never been dyed, processed or had any heat tool applied to it - and be told 3 weeks later it's time for a 'trim'? How is it the hairdresser shows me exactly how much length they intend to remove off the ends, and an hour later have triple that amount lying on the floor? Is it because I have an extraordinarily long torso and am very tall with a very long neck so they can't tell how much they're cutting because their reference points are off? What am I supposed to ask for when I get a trim? What am I doing wrong? I hate this length. Should I just go every 2 years instead of every six months? I'm getting fed up of always paying for a service, giving a tip and being left with sad hair. Like I'm 30, I'm past the age where I cry about bad hair cuts, but I'm also just like, at what age am I going to be able to enjoy the hair salon and not have it be some awful chore where I feel robbed every time?

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