Asian is such a broad category though. There are 48 countries in Asia and virtually all of them have different languages and looks. An Indian actor is very different from a Vietnamese, Chinese, Japanese, or South Korean actor. Most of the time when the internet says asian, its really short hand for "chinese or japanese" it feels like. Even then, it gets even more complicated when you factor in what we are really talking about is Asian American actors, who are going to be of mixed race many times. Tiger Woods and Nicki Minaj and Bruno Mars and Rob Schneider (yes, his mom is Filipino) and Norah Jones and The Rock could all be considered Asian American.
A typical blockbuster tentpole movie reason given why asian's are cast as leads is the idea that in Asia itself people will view white characters as "neutral", but in China a Japanese actor may be viewed as box office poison, or in India a Pakistani actor would be viewed similarly (and vica versa). Seems like a bullshit reason to me but I've heard it a few times, also applied to black actors. Feels like movies like the Fast and the Furious and comic book movies though are slowly breaking down that prejudice.
Be interesting to see how Black Panther does worldwide next year, not just domestic. More and more for movies, international sales are vastly dominating over domestic - Fast and Furious for example made $225m in USA, but over $1 billion overseas. Despicable Me 3 was $260m dom, $750m intl.