If I move from Gmail to Outlook, I can still email my friends but I can't go back and search our old conversations unless I export everything from Gmail to Outlook. If I switch from Facebook to Instagram, I can still message my friends but I can't see all of the pictures I posted on Facebook unless I export the pictures from Facebook to Instagram, but even then there are a lot of features of Facebook that I can't export data from because they just don't exist on Instagram.
History creates lock-in, and history is really hard to move around.