Because they - the producers - sure don't seem to have bothered.  Didn't bother getting an actor the right age - Andre 3000's 15 years older than Hendrix was at the time the movie's set.  Didn't bother leaking a clip that's actually about Hendrix.  And - most ridiculously - they made it without using ANY of Jimi's music.  Yep.  The Hendrix family wouldn't let them.  I'm all but certain they withheld for selfish reasons, but do we really need another flick about a star made just because we have another star who kinda looks and sounds like the guy? 

Watch a clip of the movie