The reason is probably because you make it sound like setting up a VCS is such a big deal. Hg or git require literally running a single command. It also seems

The reason is probably because you make it sound like setting up a VCS is such a big deal. Hg or git require literally running a single command. It also seems like you think the concept of branching in hg or git has a lot of overhead too. Again, it is literally one command to create a new branch and one command to merge or revert that branch when you are done. I don't understand why you think one needs a working MVP in order to use branches.