I have noticed it too. It really reminds me that I'm watching a film as opposed to seeing the
real story unfold in front of me. However, it is a quirk of the films which I take some enjoyment from. It is very amusing to see people put on accents (and, of course, this is a phenomena not contained merely by these three films but by many).
And
ninlaith, that 'Gorn line
("You cannot wield it!") is possibly the funniest of all the films.