There's also the possibility that, with an established Digital Service, feedback can be given to policy makers to improve the creation of new laws and make them more efficiently implementable. This might mean the difference between a law/policy that can be easily implemented using existing software, or something that has to be done by hand, costing billions - and those policy makers might not realise this.

Relevant XKCD, imagine this with lawmakers: http://xkcd.com/1425/