@maxbsawicky Well there are a few reasons.
Philosophically, there's that democracy thing that we want to support. Don't keep Trump off the ballot as we want to allow voters to vote for whoever they want to on the ballot.
Strategically, keeping Trump off the ballot encourages Republicans to vote for someone who has a better chance of winning the election. Maybe that's not actually a direction one wants to go.
Legally, it makes a mess of the legal system to try to jump through the hoops to justify the exclusion.
I could go on.
@maxbsawicky the threat of a Biden victory is exactly why another Republican nominee would likely prevail, according to polling.
People really hate both of these guys. The first alternative to either of them is probably going to win.
So that's the strategic side, kicking Trump off the ticket would promote a different nominee that people don't hate as much, so that nominee would pretty much trounce Biden according to polling.
@volkris There are good arguments for keeping him on. Though if there is another Republican nominee he is likely to sabotage the ticket, which guarantees a Biden victory.