I'll admit that my mental image was pew-pew lasers, but I imagine 'Alien' was coasting off the pop-culture recognition of Star Wars in that regard. Like, in the wake of 'Aliens', laser pistols seem less likely, but in 1979 I suspect people would have been okay with it.
Taking 'Aliens' into consideration, I could see laser pistols as being a space-based personal defense weapon that is perhaps designed to be effective against organic targets, but isn't going to risk going through the hulk like a bullet might.