A blaster bolt can be deflected by a lightsaber.
Assuming a blaster bolt works similarly to a lightsaber, it also cannot penetrate certain materials such as Mandalorian Iron or Cortosis.
A non-direct hit from a blaster bolt is usually not fatal, as evidenced by Leia getting hit and it's 'just a scratch'.
When hit in a non-vital part of the body, say, an arm for instance will hurt, however the wound will immediately cauterize and does not cause bleeding, so a wounded limb is therefore not fatal.
Blaster bolts are easily discharged by shields. Apparently these shields are easy to make since every Droideka has it's own, not to mention every Bounty Hunter running around with one.
Now, considering all this. Why the **** doesn't anyone use good old gunpowder.
"Because it's Sci Fi and Star Wars isn't about Logic, otherwise there wouldn't be any sound in the Space Battles and X-Wings and Tie Fighters wouldn't be as maneuverable in space."
Actually blasterfire can pierce Cortosis (After a few shots), and depending on the blaster, like Han's Modified Blaster which can blow chunks out of a hanger wall, it can pierce Mandalorian Iron and a Lightsaber can cut through Mandalorian Iron, it just takes a few whacks before it does anything.
Also I think a decent explanation is because they have armor that's usually tough enough to deflect rounds like that. Not to mention there are also droids running around a lot of which have reinforced frames that can withstand bullet fire pretty well, while a well placed blaster bolt to the head unit can fry it's circuits.
Also...if we can consider the Jedi Knight Series guns Canon, they still do use Non-Blaster type weapons like the Golan Arms Flechette Shotgun or the Imperial Repeater it's just their rare.