Lasers have very limited applications, they have an inherent line of sight limits, and even the most powerful ship mounted lasers that can do like 50kW, take a minute to boil a kettle of water away, more if you wrap it in tinfoil.

And a shot might cost $10, the laser itself cost $$$, fits only in a cargo container, and requires crazy amounts of juice.

Meanwhile a simple AA gun needs none of those things and can kill things just fine.