Is that a special case for firearms, or do you think the same of pocket knives?

A pocket knife tends not to have the chance that it could plunge itself into someone's heart from a distance. Hurting someone with a knife is a pretty active offense, especially a pocket knife. Guns can and do go off without a human intentionally pulling the trigger.

My point is that people accidentally forget to not bring / forget to bring things that are vitally important with no malicious intent.

I've forgotten to bring my wallet/keys with me when I leave my place, I've forgotten to wear my glasses before driving somewhere, I've forgotten to turn on my headlights while driving (in a well lit city, to my credit). People accidentally carry pocket knives through metal detectors.

None of these thing are something that happens to most people often, it could happen just once after years of correct routine. Theses absent-minded mishaps are just human nature. They are of course going to occasionally happen with guns too. I'm sure there are more than a few cops out there who accidentally walked through metal detectors while wearing their service pistol.

I know what you were saying. I'm claiming that it's irrelevant. After enough driving on the highway, I can forget that the speed limit is 55mph and stop signs still exist. That doesn't mean that you can excuse me blowing through a four way stop at 70mph and hitting another car just because I didn't have malicious intent.

My point is, guns are a bit more dangerous than knives, and the responsibility of the holder should reflect that.

Or forget them in the restroom, try e.g. this search https://www.google.com/search?q=cop+restroom+or+bathroom+lea..., it happens quite frequently.