Pro Git

One point of view on this is that your repository’s commit history is a record of what actually happened.
It’s a historical document, valuable in its own right, and shouldn’t be tampered with.

From this angle, changing the commit history is almost blasphemous; you’re lying about what actually transpired.

So what if there was a messy series of merge commits?

That’s how it happened, and the repository should preserve that for posterity.

The opposing point of view is that the commit history is the story of how your project was made.
You wouldn’t publish the first draft of a book, so why show your messy work?

When you’re working on a project, you may need a record of all your missteps and dead-end paths, but when it’s time to show your work to the world, you may want to tell a more coherent story of how to get from A to B.