Are Reflective Vests the only defense against lasers? If they are not, what would you suggest the AP value of a laser gun is?
Lasers aren't armour piercing and other armours than the Reflective Vest work normally against them.
The point of the Reflective Vest is that it is a cheap, non-military (i.e., not black market) armour that is super-effective (+10A) against laser weapons. Since it gives +0A against everything else though, it's only a meaningful piece of armour in settings where laser weapons are common enough to make it a useful choice.
Like many things in Savage Worlds, this is very setting-dependent. While the Laser Pistol in the Savage Worlds Deluxe core rules does 1-3d6 with no AP, the Hellfire Laser Pistol in the Interface Zero (version 1) rules does 3d8 with AP 5. If I were to create a Classic Traveller setting, then I would at least seriously consider having lasers completely ignore all armor except Reflec and Ablat.
 IMO, the laser stats in SWD core are balanced for a very-near-future setting, not for a sci-fi setting in which lasers are meant to be viable as standard combat weaponry. If you're asking this question, I would suggest that you consider coming up with your own energy weapon stats rather than using those in SWD core.