They need to recoup a large proportion of the money they've spent to digistise them,and until they do they will not include them in the subscription packages.
It is not just the costs to digitise the records, Findmypast have invested hugely in the cost of conserving nearly 7000 volumes that form the 1939 National Register.
In addition they have covered the cost of creating the official digital record, indexing more than 40 million individuals listed in the records as well as providing a complex technical solution which enables the redaction of closed records from each image as necessary.
This multi-million pound project was on a significantly different scale and complexity from all previous digitisation projects and completed without any public subsidy something the National Archives could not have done alone.
Cheers
Guy