I take your point although Wimbledon to Edgware Road is only 6tph for example
On the approach to the platforms there it would be useful to know if there is time to linger to pick up a paper, buy something from the shop; just as in Stratford where the Jubilee Line platforms show how many minutes are left.
This is something that should come in with the new system, but not until then. Although in theory the platform numbers should be as timetabled, service disruptions can mean that this doesn't happen. As with Hammersmith, the TDs are set manually by the Wimbledon (NR) signaller, although at Wimbledon drivers must also operate the Train Ready To Start plunger at the head of their platform also. Thus it is harder to provide countdown information.
If you did miss a train by the time you got your paper etc. it wouldn't be too long before the next one (in the grand scheme, ten minutes isn't long), or you could always seek to connect to a Circle via the cross-platform interchange at Gloucester Road.
If you've got your hot coffee and rush to catch the train and slip, trip or get trapped in the doors it won't end well (again... I've seen far too many accidents. It really, really, really isn't worth it).