Assuming your talking about a library and not a list, the short answer is no, there is no reason to promote InfoPath fields that are not present in the document library.
The long answer is that logically this shouldn't even be possible to have promoted fields that arn't present in the library since the purpose of promoting fields is to sych data between the form and the library.
Unfortunately, it is very easily possible, because once a form has been published, changes to it's promoted fields will not be pushed to the existing content type in SharePoint. So to get them in SharePoint, you need to delete any form libraries using the content type, the content type itself, and any site columns from promoted fields. Then republish the form.
This is hardly practical in a production library since before you can do that you'd need to delete all of your data.
But if your users have been getting by without this data in SharePoint all this time, the fields never should have been promoted in the first place. Unfortunately, people tend to promote everything instead of giving some thought as to what really needs to be exposed in SharePoint views.