I have written here multiple times for years about this. Put Ascot and my username into the search and you will find them all.
The connection time at Ascot used to be 10 minutes. It was common that if the fast lines from Clapham Junction to Barnes were closed (all too frequently, including Network Rail holding their works trains on them) the Reading train would be delayed about 10 minutes by the stopper ahead, not make any time up, get to Ascot still 10, and yet again have people running for the connection having the doors slammed in their face.
For those who bleat on about how "all" the other passengers will be inconvenienced by waiting, there's hardly any local traffic starting westwards at Ascot; if there are not connecting passengers on board the Camberley/Aldershot train effectively leaves empty. The majority of the branch service users are those connecting at Ascot.
Actually, I blame Roger Ford in Modern Railways magazine, and his self-publicist "Golden Whistles" annual award, which works wholly on recorded times of trains against the timetable, in a league table to fractional percentage points, and doesn't give any concern to how connecting passengers may have been inconvenienced. The managers who get their smiling faces in the mag at the awards don't seem the sort who give the connecting passengers left on the platform to achieve these accolades any concern.
I did once read that the short Stourbridge shuttle, when operated by a single diesel car, had a comparable issue, but would leave on time from Stourbridge Junction, quite empty, even if the delayed inbound connection could be seen running in, get to Stourbridge just a couple of minutes later, record an on time arrival for the statistics (the important bit), then go straight back as an extra unscheduled service and pick the passengers up to avoid them having too much delay on a cold winter evening!