It took whoever it was an age to install new card readers at Abbey wood on the Elizabeth line platforms (left off the original plans I think), which may have been complicated by contractual issues. Someone will be along to clarify but I think extra readers may be the least likely solution.
Why aren't oyster card readers actually on the trains?
How would they know where you got off ? Or if you just tapped out but stayed on ?
A reader system operates on many tram / train services I have used on the continent, so can be done. Your point about tapping out and staying on is the same as anyone abusing the system. There is a threat of a conductor coming on and catching you out, but it’s relatively simple to enter most suburban stations now without having to go through a gate.
Comments
At least a couple of extra card reader points are needed. Same goes for London bound platform.
Small plus was pre-match Kent bound platform did open an extra gate to allow pre-paids straight through but this was only used by a few people.