As someone who has many projects and non-infinite free time, choosing projects wisely is important. Others will obviously have different priorities.
That said, I will never have such a veils/lines/prefs tool on my game because I feel it foists a level of responsibility onto storytellers that I am not comfortable accepting.
If you put "triggered by spiders" in your profile, and I somehow miss it and I put spiders in my scene, I don't want you coming at me all: "I had this in my prefs profile WTF is the matter with you, you monster - you caused me a RL panic attack."
I refuse to accept responsibility for someone else's mental health while playing a game. We're all adults. I will be considerate and accommodating to the best of my ability when someone raises a concern to me directly, but I'm not comfortable with the impartial and potentially unreliable nature of relying on a tool for such important communication.
Again, that's just me. If someone wants to use such a tool on their game and accept responsibility themselves - that's their business.