I wish people, especially railway management, would find a different name instead of "leisure" for travel that is neither (company) business nor commuting, as it implies the travel is optional and passengers can use advance tickets and/or pick and choose the time they travel. Much of such travel is on essential personal business, often urgent. For example I would not call a funeral a "leisure" activity. Nor is a hospital appointment. In neither case do you get much choice in the timing.
In the context of long distance travel to and from London, most of it will be business or leisure. Some local rail travel will be essential shopping, medical appointments etc, but if you're travelling from Milton Keynes to London for shopping it's probably not to food or to travel to the nearest shop selling shirts or kettles.
Most users of peak rate or "anytime" tickets are not business travellers, who can plan their meetings in advance and in my experience get the 3rd degree from their T&S departments if they try to use anything other than an "advance" ticket - (they also require us to book through the Trainline, which makes changes and refunds more complex - and of course you pay their booking fee - but that's another story).
I don't know what type of company you work for but the types of businesses I've worked for can't schedule in meetings for specific times 2-3 months in advance and expect those times to remain unchanged. I had a provisional date in my diary for London this coming Wednesday, it's now been moved to 1st November and the head of department has said train tickets can't be booked before 19 October as it's possible the date will change again.
Even if the date was confirmed 12 weeks in advance there would be some team members arriving on Avanti, some on East Midlands Railway, some on GWR and some on LNER. Trying to find cheap Advances that allow everyone to arrive and depart at similar times would be almost impossible. Making allowances for different peak/off-peak restrictions on different routes is difficult enough! That's the effect of post-COVID hybrid/remote employment - not everyone is in the same location anymore.
The only times I can recall travelling long distances on an "anytime" ticket were on very urgent personal business - as neither of my parents gave me much notice they were going to die and I lived, at the relevant times, 150 and 300 miles away from them. To call such mercy dashes "leisure travel" is worse than insulting, and the high prices demanded for such journeys is exploitative.
What you're describing is extremely rare. A parent dying happens, at most, twice in your entire life. I've lost one parent and it didn't result in me making a single rail journey. I've made around 10 business trips by rail since joining my current employer. 4 involved buying Anytime tickets for short journeys and 6 have involved buying Off Peak Returns for London.
I'm surprised there hasn't been more media coverage.
It was on a Sunday. If it had been a weekday there would have been many journalists reporting on it on their own social feeds, as they would have been stuck themselves.