I’m not sure why so many states have these unofficial contests. They’re probably a fair indicator of which way the official vote will go but they seem kind of pointless aside from that.
I'm guessing it's to add a bit of GOP-e propaganda to try to keep the RINO's floating with the other turds.
Political parties are (more or less) democratically operated organizations. They must meet to choose officers and rules. Outsiders just see straw votes. Those that are there see what like-minded neighbors are thinking about a variety of issues. Candidate preference straw votes inform leaders of members’ desires for the future and add some excitement.