system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why aren't the U.S. Presidential Primaries rotated so that other states have a chance to go first?

It seems that by April the choices essentially are made and many states never get to select among a full slate of candidates.
gpt
There have been many proposals to do just that. But there's a few things to remember:

1. Primaries aren't just for Presidents: they're for all the offices later that November. States are more or less bound by law when primaries are held. In practice, of course, states can basically do whatever they want; witness Michigan and Florida in 2008 who went against the DNC and had their delegates stripped (which conceivably could have given Hillary Clinton a boost over Obama).

2. The first four states (New Hampshire, Iowa, South Carolina, and Nevada) weren't chosen by accident. They represent each of the four regions (North, Midwest, South, and West) and most are small enough to make it competitive. If the first state was New York, Texas, or Illinois, only well-financed and connected politicians are going to win. Basically, these first four primaries are a reasonable test that most candidates can afford to compete in. 

3. After these first four is Super Tuesday, where multiple states (usually around 10+) are done at once. 

It's a difficult balance. You don't want to have all the primaries at once, because that doesn't give voters a whole lot of information to digest. You don't want big states at first because you want most of the candidates, even smaller and less well-known ones, to at least have a chance. But you also want a candidate who has the organizational skills to handle multiple states at once and to win a state that doesn't require going door-to-door. 

Basically, you want a candidate that can handle multiple different scenarios. Organization, fundraising, retail politics, media savvy, and state-level support (i.e. interest groups). Someone who can win in both big and small states, and can win in multiple regions. That usually does a good job of vetting candidates who are ready to go on to the general election. 

So, to answer your question: they can (and probably should) rotate the states around, but there's only so many states that fit this particular pattern. It's probably more trouble than it's worth.