I know that I'm not the only person that gets irritated by all of the book haul videos on YouTube where Booktubers show off all the books that they have bought or been sent by publishers or viewers. Many of them know that the more books that they show off in a haul the more views that they will get, so there is an incentive for them to film massive book hauls that would be hundreds if not thousands of dollars worth of books. It's not the fact that many of the books that get shown weren't actually purchased by the Booktuber but the build up of hype around books that many of the people wouldn't normally purchase immediately. The level of FOMO (fear of missing out) that is unnecessarily created by showing off the books that have just been released often puts a financial strain on those watching these videos.
I have personally fallen into the trap of buying these brand new releases because of Booktube when I know that I am not going to be reading them immediately. Often if I wait a month or two after it has been released, I can find it through my library. There are some books that I know I will want to own a copy of because perhaps I want to annotate it or will want to read again but many books I read I don't need to have on my shelf after I have read it.
I don't find the book hauls that are books that came from used book stores or libraries to be harmful because it isn't promoting a level of hyper-consumerism that all new books do.
There is also the pressure that many people feel to have aesthetically pleasing bookshelves filled with hardcover copies of all their books. This creates another level of unnecessary consumerism. Many people actually prefer to read the smaller paperback copies of books because they are easier on their wrists.
I personally love to buy my books used if I can because I am the kind of person that will regularly get rid of the books that I have read and know I won't read again. I used to just donate them to my local library for the used book sale (which is where many of them came from in the first place) but I haven't been able to do that for the last year and a half. Now I have been selling my used books (and sometime not used/unread) on Depop. That has actually been very successful because I am able to get some of the money back I spent of these books in the first place.
The harm that comes from book hauls is a psychological harm that can come from the belief that those watching must buy the books that are being shown because they are what is popular, whether or not the person buying the book may actually like it or not. Also, a level of harm from a consumer/financial aspect, since there may be people putting themselves into debt in order to get more views or likes on their videos.
