Assumes nobody's changes ever collide or conflict with each other.
Introduces a fear of refactoring and making improvements as you go as that increases the risk of a merge conflict.
Delays discovery of changes being made where you might be able to have some positive input until the work is 'finished'.
I don't believe that anyone using any VCS expects every single commit to be free from "conflict" or "change collision".
In fact, the whole point of using VCS is that "conflicts" and "change collisions" are a given, thus there is a need to use a specialized tool to manage merges and handle conflicts.
> Introduces a fear of refactoring
On who? They have the exact opposite effect.
Have you ever actually used any version control system?
And, yes, I have! SourceSafe, CVS, StarTeam, Subversion, Perforce, ClearCase, PVCS, Mercurial and Git in (roughly) chronological order by my reckoning. Thanks for asking.