Primaries cost the state money whereas I believe the caucuses are solely paid for by the political parties. So, some states will likely balk at this, at least initially.
Yes, which is why I am completely opposed to primaries. If showing up and putting in a bit of effort to caucus every 4 years is something you have a problem with, switch to an instant caucus system like the GOP has in many states. The state has no business in paying for or being involved with internal elections of private political parties.
