Star Wars universe does have lasers of all scales and power levels.
Yet literally no one uses them well on a personal scale.
The Jedi (and Sith for that matter) imbue it with a power of magical stone, and then…use it as a saber.
To balance this stupidity, stormtroopers, clones and droids all use slow, non-continuous energy blasters. With actual lasers, they could insta-kill any Jedi, but they cannot, because otherwise the movie wouldn’t exist.
Because it’s cheap and looks scary. The Empire controls through fear and perceived power, not actual technological superiority. Stormtroopers primary job is to suppress dissent in civilian populations, they generally aren’t fighting an opposing army.