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.
And why the hell do the stormtroopers wear all that armor if one shot kills them?
The actual answer is that faceless pawns make better canon folder villains because it’s less likely the audience will relate to them as actual people in the context of the narrative. The in-universe explanation is that faceless pawns are better foot soldiers for the empire because it’s less likely said empire will relate to them as actual people.
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.
Because they tend to bump into things an awful lot.
It does deflect/disperse some of the energy, how much depends on what kind of plot armor you are wearing beneath it.