Quoted:
If you do miserably in Iowa, you can forget about that last few weeks of incredible expense and hardcore campaigning in New Hampshire. Or not. But at least you get the option.
Trying to campaign in all states at once would cost as much as running for the actual presidency and be just as much of an effort. And the results would be much less clear, as there would be so many candidates in so many states at this early stage where a lot of people barely know who is running that you'd have a bunch of meaningless results. Running them sequentially narrows the field.
Not saying it is best, just pointing out whatever benefits I see.
With the advent of newspapers, radio, television, computers, the internet, blogs, Youtube, twitter, iphones and ipads, I think old-school campaigning is a thing of the past. If I want to learn about a candidate, there are 87 ways I can do it that do not include seeing them at a town hall meeting or political rally.
With the staggered primaries, the people in the latter primaries simply have votes that do not count.