Keyhan -
Yes, Martin is very good so I think he's probably correct about the Hardware ID being what the purchases are tied to. I would think they'd use this as another in a long line of pushes to get us to use Microsoft Accounts, but they must want to be able to sell to those who only want Local Accounts and this is how they came up with you being able to access your purchases going forward. Of course if you move to another PC then you'd need a MS Account associated with it first to get them to migrate.
If you want to express your opinion on this you may be able to help Microsoft improve this product/experience by using the Feedback Hub in Start Menu, especially if you are comfortable with sharing relevant data and screen recordings. Microsoft developers DO read feedback from customers that comes in via the Feedback Hub, so that is a great way to share your thoughts on how to better serve you as a customer.
If you want to post back a Share link from your Feedback, others can vote it up and add to it to try to build momentum to get the developers to act .