> Even in movies where everything is explained e.g. in Blade where they will have a scene where someone explains how a weapon works, I've noticed in a recent viewing of the movie that people forgot the explanations of the gadgets he has. In Blade they have a James Bond / Q like conversation between the characters to say "this weapons does X against vampires" and sets the weapon for later on in the movie and people forgot about it.

That’s because you’re seeing the rule of cool in action. The explanation itself makes the item interesting enough that the (2 seconds) setup gets the audience excited up watch a grenade blow a vampire’s head off.