Another of my curiosity questions
I can usually get an e ticket travelling from Ramsgate. Going to Eastbourne on Monday and only paper ticket available. No problem at all but just wondered why
Is it because it's across two Tocs?
E-Ticket availability for all retailers except Trainline is controlled directly by the train companies.
They need to enable flows (combinations of from/to and route) for E-Tickets manually in a system named RCS.
If that system says you can't sell a particular ticket as an E-Ticket, it has to be offered on paper instead (or an alternative like smartcard or m-Ticket where applicable).
Most flows which are valid across London aren't enabled (there are exceptions, such as some Thameslink tickets which are technically interavailable on the tube), and various other flows aren't, typically by accident.
(Ticket types also need to be enabled for E-Ticket fulfillment too, but this is, at least from my experience, generally less of an issue.)