Primaries cost the party a lot of money -- money they can use to win races in the general election, including President.
Primaries are run by the party officials in each state.
Primaries are not necessary to pick a nominee. That's done officially at the convention via delegates. Delegates usually cast their votes based on primaries but that's not mandated.
Canceling a primary is not the same as rigging the primaries for one party-preferred candidate over the other. I don't expect you to agree, because if you did, you wouldn't have made such a stupid comment.
Canceling is a transparent decision, while rigging the primaries is a sneaky tactic that wasted not only the party's money spent holding the primaries, but also Bernie's donors' money. They donated with the belief that Bernie had a fair shot at being nominated. Canceling avoids the dog-and-pony show (and expense) when the outcome is already a given. It's the smart path to take for everyone concerned, especially for the voters who send their hard-earned money to candidates hoping they'll succeed.
This is nothing like the Hillary/Bernie debacle.
Hillary lost votes because a good number of Dems were supporting Bernie, either because they liked his policies better, or they simply hated her as a candidate.
Once Hildabeast won enough delegates and was guaranteed the nomination, most Bernie-Bros became soured on voting for her. There was also a good number of Hillary voters who decided to not even vote because of the email scandal, her demonization of half the country as deplorables, and obviously the rigging of the primaries.
As usual, your "opinion" of what's happening re: GOP and Trump is not based on actual facts. You can spin this however you want (as are the Liberal media hacks), but there is no similarity at all.
We aren't talking about running for 8th grade class president. These primary elections, campaign ads and opportunity costs (money they'll need to use in the general) are huge. Wasting all of those resources to paint a picture of "fairness" when Trump WILL BE the nominee barring any health issues would be unwise.
If the DNC wanted to waste the GOP's war chest, running a candidate with no chance of winning in the GOP primary -- just to force a primary to be held -- would not be beneath them. These are PARTY primaries. Any real Republican wanting party support in the future won't be challenging Trump.