Neil Williams wrote:

The solution to all this is to remove all situations (other than
equipment failure) where you'd legitimately touch in using an Oyster
and not touch out. This would be done by changing paper BZ extensions
such that they are valid for any journey from inside the Zones the
Travelcard is valid for to the specified destination, but are shown as
only valid when carrying the specific numbered Oyster card shown (and
checked) at purchase (to prevent double-use).

It's a solution but it doesn't take into account the number of stations that
are simply not physically designed for the peak hour crowds to all have stop
to use readers, let alone barriers. My local station, Forest Gate, is just
one where the evening crowd is so big that I can easily see chaos, fights
and people risking their lives by crossing the fast tracks to the quiet
platform all for the sake of getting out of the station quicker rather than
waiting an eternity to squeeze through a narrow hallway with only a couple
of readers - and having to deal with London bound passengers fighting to get
to their own platform. The station just isn't designed * for that and for
that matter it will also create problems on the trains and at Stratford
because even more people will be trying to wedge themselves into the front
carriages in the hope of getting out quicker. Until the station, and many
like it, are designed to make the crowd flow smoother, requiring everyone to
touch out will be utterly unworkable.

(* Actually when originally built Forest Gate was actually reasonably
designed for this because stopping services used what are now the fast
tracks and vice versa. On that configuration the evening peak crowd would
have used platform 4 which had both its own staircase to the ticket hall and
also a ramp to a direct street exit. The staircase has now been bricked up.)