I could also imagine aliens that might see in different light spectrums and our visible light spectrum is 'dark' to them, like how we would perceive infrared, microwaves, or radio waves without giving a second thought as to whether or not something unknown might be able to sense that random spectrum emissions. Maybe they see in microwave range, maybe they use the light spectrum much like we use our radio spectrum and just blindly broadcast it in mass quantity as line-of-sight communication technology. Maybe it is used as a scanner/detector beam source, like how we might x-ray rock samples or something to determine composition.

But beyond something crazy like that, yeah it doesn't make a whole lot of sense to be spewing light as an alien visitor.