Peter Campbell Smith wrote:

For various bits of NR, eg Hampton Court, Epsom Downs (PAYG not
accepted) they've extended zone 6.

I think that Hampton Court has been in the zones since zones were
invented,

I believe this is so. Although the station is outside Greater London its
catchment area stretches into it (including the palace itself).

but Epsom Downs and Tattenham Corner (both arguably in Epsom)

IIRC both are on the actual border between Epsom & Ewell and Reigate &
Banstead.

were added
recently. Although the users of Epsom station would welcome its being
included in zone 6, I have seen no official encouragement to think that it
will be.

I would guess that more passengers use Epsom station in an hour than use
ED
and TC in a day, so the effect on revenue would be siginificant.

Yes - the Epsom Downs line has a low frequency of just one train an hour off
peak and not that many more at peak hours, and also if memory serves correct
it usually takes one of the longer routes to London. The result is that many
people for whom it's their nearest station (including my family and myself
in the past) will use Epsom instead. There's never been an "Epsom stations"
group (and I recall once discovering Sutton to Epsom is cheaper than Sutton
to Epsom Downs), though the usefulness would be limited to people travelling
from West Croydon or Sutton who could walk from Epsom Downs to their
destination.