Should traps have tells?

[pemerton]

if the hostile neighbors/invaders are kobolds, my traps need to be low, and "lethal" enough to inflict about 7 damage... which isn't a threat to most adventurers after 1st level, but in this case, I wasn't trying to kill adventurers!

I'm not sure what this looks like in the fiction, that is, what is the nature of a trap that is lethal enough to deal 7 hp damage but not more.

 

[Lanefan]

Realistic in the sense that traps are built to harm, maim, and kill rather than be easily-spotted gameplay elements.

Or delay, divert, distract, and disperse. Not all traps need to be damaging but IMO they all need a good in-fiction reason to be there. That they then become gameplay elements is merely a side effect.