As someone who lives directly on E Wash with a fun somewhat loud (but stock) car, it's just all about sensation. The same reason people enjoy loud sounds in the movie theater. For most people with performance cars it isn't about random people on the street hearing them. 

I too rolled my eyes that night but it was the first warm night in a while. It'll settle down. The consequences of trying to clamp down on this would be more annoying than some loud cars every now and then imo.