It's like how Nevada residents _insist_ on the incorrect pronunciation of the name of their state[1]. I go with the "when in Rome..." philosophy -- I say it wrong when I'm there, too.
It is correct because it is codified. The State of Nevada once had a very detailed web page explaining why the hard A is correct. In some state documents, you will even see it written Nevāda. (iOS doesn't seem to have the proper glyph.)
Meanwhile, both Wilkes-Barre, Pennsylvania and Los Angeles, California each have four correct pronunciations.
(I prefer the "Los Angeleez" variation because that is what I first heard on KHJ.)
[1] https://www.mentalfloss.com/article/618644/youre-probably-pr...