As an online drawing evolves, updates are generated, and with them come new versions, which are automatically saved in a history. This is very important, especially when sharing a drawing with other people.
Imagine that a user wants to know what has changed between the current version of the drawing and a previous one. The truth is that the user can find out easily, since we have tools to compare versions. We can also promote a previous version so that it becomes the current version. Can you imagine the power that this gives to those responsible for the project?