The majority of passengers are doing 30 mins or less, so it’s right that the trains primarily cater for around this length of journey. It isn’t a “statistical anomaly”, IIRC typical usage was assessed around the time the trains were introduced (
@Bald Rick will be able to confirm) so it was a known fact. Why would you discount those who only use the trains through the core?! I guarantee there are far more of those than there are people who commute from Bedford to London on the 700s.
In fact I’m one of them! My typical journey is London Bridge - St Pancras which they’re fine for. I also find the 700 seating fine for up to an hour or so, which must cover 99% of journeys. The total length of the routes is irrelevant to the useage case they’re designed for, in the same way as you wouldn’t expect Central Line trains to cater for the tiny % or passengers who travel from West Ruislip to Epping. It’s exactly the same concept with the 700s.