Someone spends months or years of their life dedicated to writing a book. And people celebrate the fact they can get it for free, justify it by saying it's not free to search or host this content and offer to donate to piracy sites.
Rather than... Just supporting the author and buying their book?
It's different when this is American education and you're effectively being forced to buy books otherwise. I can understand fighting against that. But most stuff on the archive isn't that. It's just plain old piracy.
Yes a PDF or epub doesn't cost money to "print". Yes no one is "losing" money. But this isn't Netflix or Hollywood who still making billions regardless of piracy. Most of these authors are just regular people.
And the whole preservation angle makes sense when the books are no longer for sale. It's hard to argue preservation when you're linking to or hosting these works the second they are available to download. I'd be much more inclined projects that time walled the data, so you could effectively argue it's for preservation.