Primaries aren't enshrined in the Constitution, but they became state business in the 1970s because there was a desire to let the average voter have more say in the selection process, which had previously been done via party conventions.

https://www.washingtonpost.com/news/monkey-cage/wp/2015/05/1...

I would prefer going back to party conventions instead of the endless campaigning :-)

Either way it boils down to $ spent to “win” the nomination. Whether it’s spent on advertising or back room wheeling n’ dealing it’s just money spent.