why the hell would you wear a space suit in a battle on a planet with normal atmospheric environments?
Seems pretty dumb on the Santuary moon, unless they are ensuring that they are not vulnerable to chemical warfare
. Note that the Empire had a mixture of forces there, and more than a few commando-types, so not all their troops suffered the disadvantages of the armor.
However, on Tatooine, the armor is for protection against desert conditions
From what we see in the movies, it doesn't matter that the blaster bolts don't penetrate the armor. The troopers go down just the same.
There aren't any examples in the films of anyone attempting to shoot blasters at the troopers that could even begin to support this. Unless you have any?
The armor proves vulnerable to stone age weapons, but that has no bearing on the issue of the strength of a blaster shot needed to penetrate it.