We really should be enjoying the benefits of a centralised National Health Service in this country, but the divide and conquer management strategy gives individual GP practices and Hospitals (run by NHS Trusts) a lot of independence. That independence extends to IT systems, meaning you have various patient record systems in use around the country and a set of standards and APIs mandated to allow them to communicate.
I would personally prefer those patient records to be on software provided and administered by a technical organisation with the expertise to understand the security risks involved and working full time on that problem. Hospitals and GPs could then get on with treating patients rather than having to employ their staff to figure out the tech side. So why isn't NHS Digital doing that instead?
I expect most people actually believe the NHS already have their medical records, and in a sense they do, it just has many different custodians all around the system.