It's not, hence why they didn't do it. The Secret Service does need to protect trump for the rest of his life, unfortunately, since he was a US president, and he was never held accountable for his ten thousand crimes as president.
The DNC and RNC are organizations, there's no reason outside of organizational preference for them to hold votes... They could flip a coin for all 'voters rights' are concerned. They are literally just fundraising organizations that pick someone to throw money behind.
Party affiliation, for all intents and purposes, shouldn't even be listed on the ballots and the only reason they are is because the two parties realize splitting the country is a better way to raise funds than any amount of policy or good intentions.
based on his performance at the debate, we can clearly say Biden isn't a threat to anyone. It is the DNC and others that are the threat. Biden doesn't even know where he is most days.