Turbotax forms updates

Why must I install Turbotax forms updates after I have filed my returns?  Is it possible that these changes will change the tax returns that I have already been filed? Why is it so difficult to find out what the form updates are about?  It sends us out to the community where it is virtually impossible to find the answer.

When I have Turbotax Business and Turbotax 2018 on the PC, why does Turbotax Business open when I select my personal return from the desktop?