Trigger warnings have been quite heavily researched at this point and at best they seem to have no positive impact to overcoming traumatic events and a some of the studies have shown them to be a negative.

Put 'scientific support for trigger warnings' in your favorite search engine and you'll find meta-analysis, RCTs, other types of studies, reviews, as well as discussions from the APS, other psychology and psychiatry related publications, etc.

This isn't to say removing trigger warnings is a replacement for actual guided therapy, exposure therapy or otherwise, but it doesn't seem like it would be a negative outcome for long term mental health and would be a benefit for anticipatory distress and potentially in combating avoidant behaviors (though not all studies universally found them to increase avoidant behaviors - just some)

This is a separate question than when it comes to general polite society and social expectations and what is and isn't considered a courtesy. The studies also aren't dealing with people that have just gone through the traumatic experience, so you could make a reasonable argument that exposure to something still fresh could have a very different impact.