It's a Charlie Brown and the football situation. You can only fall for the same bait and switch so many times before you just give up. In a democracy it leads to voter apathy. And primaries are poorly run. If it isn't a prominent one, you likely won't find much information on the candidates prior to the primary election, and for the president, they sre pretty much decided by 4th one so if you're state does a later primary, chances are that your preferred candidate has already dropped out by the time you can actually vote for them.