To enable building solutions that use impersonation, for example a logged in manager/superuser selecting an employee/user and managing that employee's cart, adding/removing items and browsing the site/shop from the employee´s point of view.
See forumpost for more details,
https://forum.litium.com/t/how-to-implement-impersonate-superuser-impersonate-another-user/765
This is a feature we are very interested in for our B2B customers who have a support team or sales reps who want to place orders for other organisations. So the order gets placed for the customer and not on the sales reps account.
Same for support line who needs to debug an issue where a customer might not see the right price for a product or not see the correct products on the site.
Today we have to make workarounds like making endpoints to place the suppoert/sales rep as a member of the organisation temporarily, which is a bit clunky and does not really impersonate the user, and instead just the organisation.