Alright, I'm a do a bit of research on these guys:
Taylor Kitsch: was in Friday Night Lights which was sort of popular and critically acclaimed. Snakes on a Plane helped (ok not). For John Carter, remember he was just getting off his Friday Night Light's high similar to how Bryan Cranston or Idris Elba HAVE to be in every movie since The Wire, Breaking Bad, and Luthor. He has fizzled a bit since those days so he's no longer as bankable as we may think.
Sam Worthinton: he had 11 movies before Terminator Salvation which he wasn't the main character. He did put in his due in some recognizable movies to eventually land himself a co-star role against Christian Bale in Salvation. Avatar came out the same year but this isn't a movie led by Sam Worthington but James Cameron. You could have replaced Jake Sully with any random mother fucker and it would make the exact same amount of money. Even Idris Elba.
Armie Hammer: similar career start as Sam Worthing except he had Social Network cred and J Edgar with Leonardio DiCaprio. It doesn't strike me as too odd he would eventually get cast for a big budget movie. The Lone Ranger does seem to lean towards Jack Sparrow, though. Since those days Mr. Hammer doesn't seem to be handed any lead in big budgets, though.
Chris Pine: not sure, maybe he sucks a mean dick because his info is quite odd. I'll give you that.
Hugh Jackman: his breakout role was in an ensemble blockbuster movie that cost $75 million to make. The studio took a very low risk.
They're not virtually unknown (except Chris Pine -- how that fucker do it?!), they got a decent portfolio behind them and the ones who do perform well seem to have continued success. But folks like
Taylor Kitsch and
Sam Worthington (unless a new Titans movie comes) and
Armie Hammer aren't exactly getting big leads in blockbusters nowadays.
ScarJo has a decent portfolio behind her that makes be bankable to a degree (jn their minds).
Like, no one's knocking on Mr. Hammer's door to sign him up to lead in the next unknown franchise movie that costs $200 million.
Like, I'm not saying whitewashing doesn't exist or Hollywood isn't biased against Asians or other minorities due to the perceived lost profits but it's not like 100% of all white leads are handed big budget roles for no raisin, they all were visible at some point. The whiteness part really only seems to matters when comparing two capable candidates but the studio takes the white person. Except Chris Pine.