It seems to me that a lot of people are viewing trigger warnings as a thing someone reads and then says "gosh, that sounds scary, I'm not going to read this book now."
My experience is that most people who use trigger warnings (I'm not one of them, so my experience is limited) read them and say "ah, good to know that this is going to be a thing; now I will be prepared for it."
I'm actually coming at it from the sample place you are, but I don't see it as a benefit. At it's most innocent place, I see it as a spoiler (even in topic only). At it's worst, I see it as the world placating a person's weakness to adapt to the situation. A big chunk of life is learning that you will not and cannot be externally protected from challenges, harm, or hardship. That instead, you have to teach yourself to deal with the issues of in the world around you...both planned for an unplanned for.
~Jeordam
Saving the Princess, Humanity, or the World-Entire since 1985