[quote name='Jus Lukin' timestamp='1499177509' post='3329720']
Quite. A vocal has a range. A song which sounds great with one voice (the one of whoever wrote it, say) might sound wrong with another. A shunt in one direction or another might bring the song alive for the singer in question.
A far better thing to ask might be about why some musicians are so fixated on the importance of the key a song was originally written in.
[/quote]
This. In spades.
The OP reads a lot like someone who has never sung.
It's akin to demanding that a bassist play a low D on a 4 string tuned EADG.
What do you mean you can't do it? What do you mean your instrument doesn't do it? Why are you crap at your instrument?