The regular lead bullets from even a small caliber short barrel weapon is too fast for eyes to see. But the speed of light phasers being fired by the storm troopers leave a neat clean visible tracer lines. That leads straight back to the location of the gun which helps Harrison Ford ample time to find good spot to dive into, no antique plane needed.
I can't believe I'm replying to a joke post but... (a) you're mixing your movies, phasers are Star Trek and blasters are Star Wars. (b) Blasters supposedly shoot charged plasma - you fill them with gas, they excite it to a plasma somehow, and the glowing plasma is what's shot at the targets. Don't ask me about turbo lasers on capital ships.
(Cue a follow-on stream of comments correcting mistakes I've made, lol.)