The easiest way for me to articulate my thoughts on the matter are bullet points, so bear with me:

• I believe that at some point and with some subset of internet denizens in a particular community, there might have been valid concern over the idea of a trigger, that was grounded in actual medical concerns. For instance, those with PTSD and actual trauma.
• Concerns arose because of "free-flow" between niche communities that I've arbitrarily defined and the internet at large. Sites like Tumblr have the capacity to push content from very small, specific communities into a large stage and vice versa, and it's this kind of dynamic that makes sites like these popular.
• While the concerns of these small groups may be valid, to call for the regulation of these huge internet spaces is impractical and impossible, and may have been recognized early on. The concerns for triggers may have been limited to these niche communities at first, and the expectation within a small community was to abide out of of common interest.
• Just like anything on the internet, the idea of "triggers" themselves became susceptible to this natural "free-flow".
• The idea of the trigger became distorted, no longer a product of very personal concerns but of people with narcissistic interests, and people with misplaced and misunderstood concerns for those with actual issues. As a result of this larger stage, people wanted to expand on what these triggers could include to be a part of this movement.
• Thus, the trigger became this abused attempt of regulating the largest communities of the internet, no longer out of any valid concern.

Anecdotally, I have an issue that I don't feel like disclosing, and I haven't to most people, because the moment you do, people stop treating you normally. There are things, content, comments, that are extremely distressing to me. The thing is, I don't expect anything on the internet to cater to me, and I don't want the false pity of people who have no actual concern or understanding on the matter. If there's something concerning, I avoid it. And if I'm hurt browsing dank memes, that's the result of the risk that I decided to take. There's a reasonable limit to precautions in scope, but no one is entitled to everything.

Here's a terrible analogy and my TLDR: There are reasonable regulations for peanut processing- label foods processed with peanuts, cafeterias should be aware, etc. But it isn't reasonable to outlaw peanuts because someone has a peanut allergy.