Why Would We Need Delegates For Nominating A Presidential Candidate?

Now, at face value there are a few obvious reasons why today the Presidential nomination process in both major parties uses delegates. It solves the question of what happens after candidates with millions of votes drop out of the race, which of course happens regularly in Presidential primaries, usually after the vote in some crucial states has proven the candidate's lack of appeal.

Something else that many people don't know - including myself until a few days ago - is that the Democratic National Convention and Republican National Convention are basically the main bodies of the parties, which the Democratic National Committee and Republican National Committee only represent during those 4 years when it's not in session. This means that unless we entirely change how the two main parties are set up, the DNC and RNC every 4 years will always need to consist of delegates, to make decisions for the party.

However that doesn't mean we can't find a different process for electing the Presidential nominee, while the delegates are still chosen separately and still decide over the party's platform and charter. One such way would be to let party members directly elect the nominee via Ranked Choice Voting. The way that works is that on the ballot voters rank their choices from 1. to last (they can also just list one). Then if no candidate gets a majority of 1. votes, the candidate with the fewest votes is eliminated and his votes are redistributed to the next choice on his voters' ballots. If still nobody has a majority, whoever now has the fewest votes is eliminated and his votes redistributed, and so on, until one candidate has a majority. This way, if somebody drops out of the race, his votes are automatically redistributed to his voters' next choices; which is arguably considerably better than when party bosses and/or the candidates themselves bribe and threaten delegates of dropped out candidates into voting for a certain nominee. One big advantage of this system over even a direct election with the common "First Past The Post" system (candidate with most votes wins), is that you ensure that the winner is actually preferred over the other candidates by a majority of voters. Ranked Choice is how Ireland elects its President, Australia its lower house, and Maine recently changed its voting system for federal elections to Ranked Choice as well.

What do you think about this idea, to nominate Presidential candidates via direct Ranked Choice Voting by the parties' members?