And people still need to buy a Network Railcard (or have an annual season ticket) for £30, so it's no giveaway for leisure travellers when you consider the Monday to Friday restrictions, especially the £13 minimum fare.
They do need to review the area though, as it makes no logical sense, e.g. Swindon being outside, and Exeter being allowed on the SWR route, but not the GWR route.
The Network Railcard may have had its origins with NSE, but the NSE/Intercity divide has been irrelevant for nearly 30 years now, yet the area hasn't been modified to reflect this.
Swindon as I mentioned, is surely more "southeast" than Worcester or King's Lynn for example. If Exeter is included, then it makes no sense for it to be only included if you go from Waterloo rather than Paddington.
The area is perfectly logical, in that it largely reflects where BR's Network South East sector was the main operator of services pre-privatisation - an area that was dictated by BR's internal operational considerations, which is why the likes of Waterloo to Exeter and the King's Lynn route were included. And the intercity/suburban operational divide remains a factor to this day, eg Avanti/LNW out of Euston, LNER/Thameslink/GN out of Kings Cross, GWR's high-speed services group and the 387/Turbo operation in the Thames Valley.
The Cotswold Line between Oxford and Worcester was a rare case of the railcard area being extended, after NSE took over the operation of most services from Regional Railways and reinstated all-day through running to and from London using Turbo sets.
Swindon was not served by NSE, nor subsequent outer-suburban services under Thames Trains, FGW Link, FGW or GWR (at least until next month with several Class 387-operated London-Swindon services being added on Sundays), while in the case of Peterborough, mentioned by 778, few passengers travelling between the city and London used the NSE services, nor the subsequent outer-suburban operators up to TL/Great Northern today (unless those passengers have a lot of time on their hands), in the same way that London-Exeter passengers travelling via Salisbury are thin on the ground.
As for Oxford-Bletchley/MK being added to the railcard zone, who knows? Bedford-Bletchley is included, but the argument could be made that the original rationale for the Network Card was to fill empty seats on off-peak services to and from London, and the East-West route does not fit in with that idea. As it will be operated initially by two-car Class 196s, there may not be all that many empty seats to fill anyway and I expect the DfT will be determined to maximise revenue from day one, so permitting the railcard might not fit with that approach.